Group 5 metal complexes for catalytic amine functionalization

ABSTRACT

This application pertains to group 5 metal complexes having the structure of Formula I: 
     
       
         
         
             
             
         
       
     
     and their potential utility in catalyzing α-alkylation of secondary amine-containing moieties.

FIELD OF THE INVENTION

This disclosure relates to the use of group 5 metal complexes for amine functionalization and synthetic process for manufacture thereof.

BACKGROUND

The catalytic functionalization of alkenes represents a sustainable and efficient method for the synthesis of molecules that are relevant for the chemical, pharmaceutical, and agrochemical industry. Such organic transformations are attractive as valuable building blocks, which are obtained economically from relatively inexpensive starting materials. Notably, the direct C—H functionalization of amines with alkenes, or hydroaminoalkylation, has gained notoriety due to the fact that polysubstituted amines can now be easily obtained in the absence of any protecting/directing groups or photoinitiators.¹

It is known in the art that group 3 (Sc), 4 (Ti, Zr), and 5 (Nb, Ta) metal complexes may serve as powerful precatalysts in hydroaminoalkylation reactions. For example, N,O-chelated pyridonate tantalum based complexes were shown capable of reacting with sterically demanding internal alkenes and facilitate their reaction with secondary anilines. These reactions occurred in a 100% regioselective manner to give the branched products.

Despite the high demand of simple and economical methods for synthesis of amine building blocks in the chemical, pharmaceutical, and agrochemical industry, there are known issues with the catalytic systems presently in use. For instance, hydroaminoalkylation often requires high reaction temperatures (>110° C.) and quite long reaction times (>20 h), which many catalysts are not robust enough to tolerate. Moreover, substrate compatibility of these catalysts is known to be problematic, especially for internal alkenes such as cyclohexene and cyclooctene. The fact that excess alkene (at least 1.5 equivalents excess) is needed to achieve full substrate conversion remains a challenge as well.

In the case of the catalytic systems, where the active species have a Ta—NMe₂ moiety, the excess alkene is often justified by the deleterious side reactions between the released HNMe₂ and the alkene reagents, thereby affecting the stoichiometry of the reaction. The use of TaMe₃Cl₂ proved to be successful, as hydroaminoalkylations of amine and alkene substrates was achieved using this catalyst in stoichiometric amounts, but with the caveat that TaMe₃Cl₂ is light and temperature sensitive and therewith not suitable for large scale industrial processes. Using a similar approach, the addition of 1-octene to 4-methoxy-N-methylaniline at room temperature was achieved with a phosphoramidate supported Ta-Me complex as the catalyst. Although this catalyst demonstrated high reactivity, the phosphoramidate Ta-Me complex actually required excess alkene in order to fully convert the substrates. To improve the stability of early transition metal complexes, steric bulk in the form of e.g. bulky alkyl groups, such as for example CH₂SiMe₃ and CH₂CMe₃, may be complexed to the metal centre. Earlier, Wilkinson and Schrock have described the alkyl tantalum complexes Ta(CH₂SiMe₃)₃Cl₂ and Ta(CH₂CMe₃)₃Cl₂. However, their activity in hydroaminoalkylation reactions has not been reported in the art.

SUMMARY OF THE INVENTION

This disclosure is based in part on the discovery of group 5 metal complexes that are advantageous for catalyzing hydroaminoalkylation reactions. In particular, the present invention relates disclosure relates to group 5 metal complexes and their use for amine functionalization, as well as synthetic processes for manufacturing such complexes. The group 5 metal complexes described herein may catalyze hydroaminoalkylation reactions at stoichiometric ratios of N-containing heterocycle to alkene and at lower reaction temperatures than those reported in the art.

Aspects of this disclosure relate to a metal complex having the structure of Formula I:

-   -   wherein:     -   R¹ and R² are:         -   each independently: H; a C₁-C₄₀ substituted or unsubstituted             linear, branched or cyclic alkyl or alkenyl or alkynyl; a             substituted or unsubstituted aryl; or a substituted or             unsubstituted heterocyclic group; or         -   bonded together thereby forming, together with the nitrogen             atom they are both bound to, a heterocycle;     -   R³:         -   is H; a C₁-C₄₀ substituted or unsubstituted linear, branched             or cyclic alkyl or alkenyl or alkynyl; or a substituted or             unsubstituted aryl; or a substituted or unsubstituted             heterocyclic group; or         -   bonded together with R¹ and/or R² to form a heterocycle.     -   M is a group 5 metal;     -   a=0 to 4 and b=0 to 4, wherein the sum of a and b is 4;     -   each X is a halogen substituent;     -   each R⁴ is independently: H; or a C₁-C₂₀ substituted or         unsubstituted, linear, branched or cyclic alkyl, optionally         comprising heteroatoms.

Each X is independently Cl or Br. IN various embodiments, a may be 1 or 2.

R¹ and R² may each independently be: methyl; ethyl; isopropyl; cyclohexyl; phenyl; 2,6-dimethyl phenyl; 2,4,6-trimethyl phenyl; 4-methyl phenyl; optionally substituted piperidine; optionally substituted pyrrolidine; or substituted morpholine.

Alternatively, R¹ and R² may be bonded together to form, together with the nitrogen atom they are both bound to, a 6-membered ring, which optionally may be substituted.

In various embodiments, R¹ and R² are each phenyl. In various embodiments, R¹ is phenyl and R² is isopropyl. In various embodiments, R¹ and R² are bonded together to form, together with the nitrogen atom they are both bound to, piperidinyl. In various embodiments, R¹ is phenyl and R² is methyl; R¹ is methyl and R² is 1-phenylethyl; In various embodiments, R¹ is methyl and R² is isopropyl; In various embodiments, R¹ is phenyl and R² is diphenylmethyl.

R³ may be: phenyl; 2,6-dimethyl phenyl; 2,6-di(isopropyl) phenyl; or

R³ may be bonded together with R¹ and/or R² to form, together with each of the nitrogen atoms they are bound to, a 5-membered ring, which optionally may be substituted. R³ may be bonded together with R¹ and/or R², and each of the nitrogen atoms they are bound to, to form:

R⁴ may be —CH₃, —NMe₂, —CH₂C(CH₃)₃, or —CH₂Si(CH₃)₃.

M may be tantalum (Ta), niobium (Nb), or vanadium (V).

Aspects of this disclosure further related to a metal complex having the structure of Formula II

-   -   wherein:         -   R¹ and R² are:             -   each independently: methyl; ethyl; isopropyl;                 cyclohexyl; phenyl; 2,6-dimethyl phenyl; 2,4,6-trimethyl                 phenyl; 4-methyl phenyl; optionally substituted                 piperidine; optionally substituted pyrrolidine; or                 substituted morpholine; or             -   bonded together to form, together with the nitrogen atom                 they are both bound to, a 6-membered ring, which                 optionally may be substituted;         -   R³ is:             -   phenyl; 2,6-dimethyl phenyl; or 2,6-di(isopropyl)                 phenyl; or bonded together with R¹ and/or R² to form,                 together with each of the nitrogen atoms they are bound                 to, a 5-membered ring, which optionally may be                 substituted;         -   each X is independently Cl or Br;         -   a=1 or 2 and b=(4−a); and         -   R⁴ is —CH₃, —NMe₂, —CH₂C(CH₃)₃, or —CH₂Si(CH₃)₃.

Aspects of the disclosure related to a metal complex, which metal complex is:

Aspects of this disclosure relate to a catalyst comprising a metal complex as defined above and elsewhere herein

Aspects of this disclosure relate to a catalyst kit comprising at least one metal complex as defined above and elsewhere herein and a quenching agent. The quenching agent may include an alcohol, water, or a combination thereof.

Aspects of this disclosure relate to a method of synthesizing a metal complex of Formula I, the method comprising reacting a group 5 metal salt of Formula VII with one equivalent of an amide of Formula VIII according to the following reaction:

wherein:

-   -   R¹ and R² are:         -   each independently: H; a C₁-C₄₀ substituted or unsubstituted             linear, branched or cyclic alkyl or alkenyl or alkynyl; a             substituted or unsubstituted aryl; or a substituted or             unsubstituted heterocyclic group; or         -   bonded together thereby forming, together with the nitrogen             atom they are both bound to, a heterocycle;     -   R³:         -   is H; a C₁-C₄₀ substituted or unsubstituted linear, branched             or cyclic alkyl or alkenyl or alkynyl; or a substituted or             unsubstituted aryl; or a substituted or unsubstituted             heterocyclic group; or         -   bonded together with R¹ and/or R² to form a heterocycle.     -   M is a group 5 metal;     -   a=0 to 4 and b=0 to 4, wherein the sum of a and b is 4;     -   c=1 to 5 and d=0 to 4, wherein the sum of c and d is 5;     -   each X is a halogen substituent;     -   each R⁴ is independently: H; or a C₁-C₂₀ substituted or         unsubstituted, linear, branched or cyclic alkyl, optionally         comprising heteroatoms.

X may be, independently, Cl or Br. In various embodiments, a may be 1 or 2.

R¹ and R² may each independently be: methyl; ethyl; isopropyl; cyclohexyl; phenyl; 2,6-dimethyl phenyl; 2,4,6-trimethyl phenyl; 4-methyl phenyl; optionally substituted piperidine; optionally substituted pyrrolidine; or substituted morpholine.

Alternatively, R¹ and R² may be bonded together to form, together with the nitrogen atom they are both bound to, a 6-membered ring, which optionally may be substituted.

In various embodiments, R¹ and R² are each phenyl. In various embodiments, R¹ is phenyl and R² is isopropyl. In various embodiments, R¹ and R² are bonded together to form, together with the nitrogen atom they are both bound to, piperidinyl. In various embodiments, R¹ is phenyl and R² is methyl; R¹ is methyl and R² is 1-phenylethyl; In various embodiments, R¹ is methyl and R² is isopropyl; In various embodiments, R¹ is phenyl and R² is diphenylmethyl. R³ may be: phenyl; 2,6-dimethyl phenyl; 2,6-di(isopropyl) phenyl; or

R³ may be bonded together with R¹ and/or R² to form, together with each of the nitrogen atoms they are bound to, a 5-membered ring, which optionally may be substituted. R³ may be bonded together with R¹ and/or R², and each of the nitrogen atoms they are bound to, to form:

R⁴ may be —CH₃, —NMe₂, —CH₂C(CH₃)₃, or —CH₂Si(CH₃)₃.

M may be tantalum (Ta), niobium (Nb), or vanadium (V).

In various embodiments, the reaction may be performed in a temperature range from −30° C. to ambient temperature.

In various embodiments, the reaction is performed at ambient temperature. Ambient temperature may be room temperature.

The reaction may be performed in an organic solvent. The organic solvent may be toluene or hexane.

In various embodiments, the method may include a further reaction step that is performed in situ.

Aspects of the disclosure relate to a method for α-alkylation of a secondary amine-containing moiety, the method comprising: (i) reacting said secondary amine-containing moiety with an olefin in the presence of a metal complex as defined above and elsewhere herein. The method may further include isolating a product formed in step (i).

The secondary amine-containing moiety may include at least two α-spa hybridized C—H bonds.

The secondary amine-containing moiety may be a C₄-C₁₀₀ linear, branched, or cyclic alkyl, optionally substituted and/or comprising heterotaoms. The secondary amine-containing moiety may be substituted with a halogen, an ether, another amine, an alkyl, an alkene, an acetal, a phosphine, an amide, an alkyne, an imine, a nitrile, an isocyanide, an epoxide, a boronic acid ester; a phenyl that optionally may be substituted and/or part of a condensed ring system, or any combination thereof.

The olefin may include from 2 to 100 carbon atoms. In various embodiments, the olefin comprises an internal alkene. In various embodiments, the olefin is a linear or a cyclic olefin. In various embodiments, the olefin comprises a terminal alkene. In various embodiments, the olefin is an optionally substituted 1-alkene or an optionally substituted cycloalk-1-ene. In various embodiments, the olefin comprises one or more protected functional group(s). In various embodiments, the olefin is:

The secondary amine-containing moiety may be: pyrrolidine; piperidine;

wherein Z is H, OCF₃, F, Cl, Br, I, or OCH₃.

The secondary amine-containing moiety may be:

The reaction conditions may include a reaction temperature in the range from 50° C. to 200° C., a reaction temperature in the range from 75° C. to 165° C., a reaction temperature in the range from 90° C. to 150° C., a reaction temperature in the range from range from 110° C. to 130° C., a reaction temperature of about 110° C., or a reaction temperature of about 130° C.

The reaction conditions may include a solvent. The solvent may be non-protic. The solvent may be toluene, benzene, or a mixture thereof.

The secondary amine-containing moiety and said olefin may be provided in a stoichiometric ratio from 0.1 to 1.5. The secondary amine-containing moiety and said olefin may be provided in a stoichiometric ratio of about 1:1.

Aspects of the disclosure relate to a method of synthesizing a pharmaceutical compound or an agrochemical compound, the method comprising α-alkylation of a secondary amine-containing moiety according to a method as defined above and elsewhere herein.

Aspects of the disclosure relate to use of a group 5 metal salt of Formula VII

MX_(c)R⁴ _(d)  (Formula VII)

-   -   wherein:         -   M is a group 5 metal;         -   c=1 to 5 and d=0 to 4, wherein the sum of c and d is 5; and         -   each R⁴ is independently: H; or a C₁-C₂₀ substituted or             unsubstituted, linear, branched or cyclic alkyl, optionally             comprising heteroatoms,

in combination with an amide of Formula VIII

wherein:

-   -   R¹ and R² are:         -   each independently: H; a C₁-C₄₀ substituted or unsubstituted             linear, branched or cyclic alkyl or alkenyl or alkynyl; a             substituted or unsubstituted aryl; or a substituted or             unsubstituted heterocyclic group; or         -   bonded together thereby forming, together with the nitrogen             atom they are both bound to, a heterocycle; and     -   R³:         -   is H; a C₁-C₄₀ substituted or unsubstituted linear, branched             or cyclic alkyl or alkenyl or alkynyl; or a substituted or             unsubstituted aryl; or a substituted or unsubstituted             heterocyclic group; or         -   bonded together with R¹ and/or R² to form a heterocycle.

for generating a catalyst for α-alkylation of a secondary amine-containing moiety.

The catalyst may be a metal complex of Formula I,

wherein a=0 to 4 and b=0 to 4, wherein the sum of a and b is 4.

In various embodiments, α-alkylation of a secondary amine-containing moiety comprises reacting said secondary amine-containing moiety with an olefin in the presence of the catalyst. The secondary-amine containing moiety and/or olefin may be as defined above and elsewhere herein.

Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

In drawings which illustrate embodiments of the invention,

FIG. 1 is a ¹H NMR spectrum (300 MHz, CDCl₃, 298 K) of 3-(2,6-dimethylphenyl)-1,1-diphenylurea.

FIG. 2 is a ¹³C NMR spectrum (75 MHz, CDCl₃, 298 K) of 3-(2,6-dimethylphenyl)-1,1-diphenylurea.

FIG. 3 is a ¹H NMR spectrum (300 MHz, CDCl₃, 298 K) of 3-(2,6-dimethylphenyl)-1-isopropyl-1-phenylurea.

FIG. 4 is a ¹³C NMR spectrum (75 MHz, CDCl₃, 298 K) of 3-(2,6-dimethylphenyl)-1-isopropyl-1-phenylurea.

FIG. 5 is a ¹H NMR spectrum (300 MHz, CDCl₃, 298 K) of 4-bromo-N-(2-methyloctyl)aniline.

FIG. 6 is a ¹³C NMR spectrum (100 MHz, CDCl₃, 298 K) of 4-bromo-N-(2-methyloctyl)aniline.

FIG. 7 is a ¹H NMR spectrum (300 MHz, CDCl₃, 298 K) of 4-bromo-N-(cyclooctylmethyl)aniline.

FIG. 8 is a ¹³C NMR spectrum (100 MHz, CDCl₃, 298 K) of 4-bromo-N-(cyclooctylmethyl)aniline.

FIG. 9 is a ¹H NMR spectrum (300 MHz, CDCl₃, 298 K) of 4-chloro-N-(cyclooctylmethyl)aniline.

FIG. 10 is a ¹³C NMR spectrum (100 MHz, CDCl₃, 298 K) of 4-chloro-N-(cyclooctylmethyl)aniline.

FIG. 11 is a ¹H NMR spectrum (300 MHz, CDCl₃, 298 K) of N-(cyclooctylmethyl)-4-fluoroaniline.

FIG. 12 is a ¹³C NMR spectrum (75 MHz, CDCl₃, 298 K) of N-(cyclooctylmethyl)-4-fluoroaniline.

FIG. 13 is a ¹H NMR spectrum (300 MHz, CDCl₃, 298 K) of N-(2-methyloctyl)-4-(trifluoromethoxy)aniline.

FIG. 14 is a ¹³C NMR spectrum (75 MHz, CDCl₃, 298 K) of N-(2-methyloctyl)-4-(trifluoromethoxy)aniline.

FIG. 15 is a ¹H NMR spectrum (300 MHz, CDCl₃, 298 K) of N-(cyclooctylmethyl)-4-(trifluoromethoxy)aniline.

FIG. 16 is a ¹³C NMR spectrum (75 MHz, CDCl₃, 298 K) of N-(cyclooctylmethyl)-4-(trifluoromethoxy)aniline.

FIG. 17 is a ¹H NMR spectrum (300 MHz, CDCl₃, 298 K) of N-(2-methyloctyl)benzo[d][1,3]dioxol-5-amine.

FIG. 18 is a ¹³C NMR spectrum (75 MHz, CDCl₃, 298 K) of N-(2-methyloctyl)benzo[d][1,3]dioxol-5-amine.

FIG. 19 is a ¹H NMR spectrum (300 MHz, CDCl₃, 298 K) of 4-((tert-butyldimethylsilyl)oxy)-2-methylbutyl)aniline.

FIG. 20 is a ¹³C NMR spectrum (75 MHz, CDCl₃, 298 K) of 4-((tert-butyldimethylsilyl)oxy)-2-methylbutyl)aniline.

FIG. 21 is a ¹H NMR spectrum (300 MHz, CDCl₃, 298 K) of a mixture between N-(2-(2-bromophenyl)propyl)aniline and N-(3-(2-bromophenyl)propyl)aniline.

FIG. 22 is a ¹H NMR spectrum (300 MHz, CDCl₃, 298 K) of 1-cyclohexylimidazolidin-2-one (^(Cy)LH).

FIG. 23 is a ¹³C NMR spectrum (100 MHz, CDCl₃, 298 K) of 1-cyclohexylimidazolidin-2-one (^(Cy)LH).

FIG. 24 is a ¹H NMR spectrum (300 MHz, CDCl₃, 298 K) of 1-phenylimidazolidin-2-one (^(Ph)LH).

FIG. 25 is a ¹H NMR spectrum (75 MHz, CDCl₃, 298 K) of 1-phenylimidazolidin-2-one (^(Ph)LH).

FIG. 26 is a ¹H NMR spectrum (300 MHz, CDCl₃, 298 K) of 1-(tert-butyl)imidazolidin-2-one (^(tBu)LH).

FIG. 27 is a ¹³C NMR spectrum (75 MHz, CDCl₃, 298 K) of 1-(tert-butyl)imidazolidin-2-one (^(tBu)LH).

FIG. 28 is a ¹H NMR spectrum (300 MHz, toluene-d₈, 298 K) of Ta(CH₂SiMe₃)₃Br₂.

FIG. 29 is a ¹H NMR spectrum (300 MHz, benzene-d₆, 298 K) of ^(tBu)LTa(CH₂SiMe₃)₃Cl.

FIG. 30 is a ¹³C NMR spectrum (75 MHz, benzene-d₆, 298 K) of ^(tBu)LTa(CH₂SiMe₃)₃Cl.

FIG. 31 is a ¹H NMR spectrum (400 MHz, benzene-d₆, 298 K) of ^(tBu)LTa(CH₂SiMe₃)₃Br.

FIG. 33 is a ¹H NMR spectrum (400 MHz, CDCl₃, 298 K) of 3-(2,6-dimethylphenyl)-1-methyl-1-(1-phenylethyl)urea.

FIG. 34 is a ¹³C NMR spectrum (100 MHz, benzene-d₆, 298 K) of 3-(2,6-dimethylphenyl)-1-methyl-1-(1-phenylethyl)urea.

FIG. 35 is a ¹H NMR spectrum (400 MHz, CDCl₃, 298 K) of 3-(2,6-dimethylphenyl)-1-isopropyl-1-phenylurea.

FIG. 36 is a ¹³C NMR spectrum (100 MHz, benzene-d₆, 298 K) of 3-(2,6-dimethylphenyl)-1-isopropyl-1-phenylurea.

FIG. 37 is a ¹H NMR spectrum (400 MHz, CDCl₃, 298 K) of 1-benzhydryl-3-(2,6-dimethylphenyl)-1-methylurea.

FIG. 38 is a ¹³C NMR spectrum (100 MHz, CDCl₃, 298 K) of 1-benzhydryl-3-(2,6-dimethylphenyl)-1-methylurea.

FIG. 39 is a ¹H NMR spectrum (400 MHz, CDCl₃, 298 K) of 3-(2,6-diisopropylphenyl)-1-methyl-1-(1-phenylethyl)urea.

FIG. 40 is a ¹³C NMR spectrum (100 MHz, CDCl₃, 298 K) of 3-(2,6-diisopropylphenyl)-1-methyl-1-(1-phenylethyl)urea.

FIG. 41 is a ¹H NMR spectrum (300 MHz, benzene-d₆, 298 K) of LTa(CH₂SiMe₃)₃Cl.

FIG. 42 is a legend of all ligands prepared and investigated in the study disclosed herein.

FIG. 43 is a graph showing the effect of reaction temperature on hydroaminoalkylation for an aryl amine.

FIG. 44 is a graph showing the effect of reaction temperature on hydroaminoalkylation for an alkyl amine.

FIG. 45 is a graph showing the effect of precatalyst concentration on hydroaminoalkylation for an alkyl amine.

FIG. 46 is a graph showing the effect of Lewis acid salts on hydroaminoalkylation for an aryl amine.

FIG. 47 is a graph showing the effect of KBr on hydroaminoalkylation for an aryl amine at different temperatures.

FIG. 48 is a graph showing the effect of KBr on hydroaminoalkylation for an alkyl amine.

DETAILED DESCRIPTION Definitions

“Catalyst”, as used herein, refers to a chemical compound that accelerates a chemical reaction without itself being affected. “Catalyst” may be used interchangeably with terms such as “pre-catalyst”, “catalyst system”, or “catalytic system”. “Catalyst”, as used herein, includes catalytic intermediates or species formed in situ.

“Group 5 metal” as used herein, refers to the d-electron comprising transition metals listed in the periodic table of the elements as group 5, including transition metals vanadium (V), niobium (Nb), tantalum (Ta), and dubnium (Db).

“Hydroaminoalkylation”, as used herein, refers to a reaction between a secondary amine containing moiety and an olefin. A catalyst may often be used to promote such reaction.

“Secondary amine”, as used herein, refers to an amine in which the amino group is directly bonded to two C-atoms of any hybridization. The two C-atoms in α-position to the N-atom may be sp³ hybridized.

“Olefin” or “alkene”, as used herein, refers to an unsaturated hydrocarbon containing one or more pairs of C-atoms linked by a double bond.

“TOF”, as used herein, refers to “turnover frequency”.

Throughout this specification, unless the context requires otherwise, the words “comprise”, “comprising” and the like, are to be construed in an inclusive sense as opposed to an exclusive sense, that is to say, in the sense of “including, but not limited to”.

This disclosure relates to the discovery that rapid C—H alkylation of unprotected secondary arylamines with unactivated alkenes can be achieved with metal complex catalysts comprising a combination of a tantalum (Ta) organometallic reagent (e.g. Ta(CH₂SiMe₃)₃Cl₂) and a ureate N,O chelating-ligand salt.

Materials and Methods

The procedures described herein are given for the purposes of example and illustration only and should not be considered to limit the spirit or scope of the invention.

1. Materials

All reactions were performed under a N₂ atmosphere using Schlenk or glovebox techniques, unless otherwise stated. TaCl₅ (Strem), Ta(NMe₂)₅ (Strem), and (chloromethyl)trimethylsilane (Sigma) were used as received. NaN(SiMe₃)₂ (Sigma) was recrystallized from a hot toluene solution before use. All amines and alkenes were commercially available, dried over CaH₂ and distilled and degassed prior to use in catalytic experiments. [Ta(NMe₂)₃Cl₂]₂, TaMe₃Cl₂, Ta(CH₂CMe₃)₃Cl₂, and Ta(CH₂SiMe₃)₃Cl₂,^(Error! Bookmark not defined). were synthesized according to literature protocols (Chem. Int. Ed. 48, 4892-4894; Synthesis 46, 2884-2896; Chem. Res 48: 2576-2586; Inorg. Chem. 20: 1859-1866; J. Am. Chem. Soc. 100: 2389-2399; Dalton Trans. 40, 7777-7782). All glassware was dried in a 180° C. oven overnight before use. Toluene, hexanes and Et₂O were dried over an activated alumina column and stored over activated molecular sieves (4 Å). d₆-Benzene and d₈-toluene were dried over sodium/ketyl and distilled prior to use. Experiments conducted on NMR tube scale were performed in J. Young NMR tubes (8″×5 mm) sealed with screw-type Teflon caps.

2. Instrumentation

¹H and ¹³C NMR spectra were recorded on Bruker 300 MHz, or 400 MHz, Avance spectrometers at ambient temperature. Chemical shifts (δ) are given relative to the corresponding residual protio solvent and are reported in parts per million (ppm). Coupling constants J are given in Hertz (Hz). The following abbreviations are used to indicate signal multiplicity: s=singlet, d=doublet, t=triplet, q=quartet, m=multiplet, and br=broad. Assignment of the signals was carried out using 1D (¹H, ¹³C{¹H}) and 2D (COSY, HSQC and HMBC) NMR experiments.

3. Synthesis

3.1 Proligands

The synthesis of proligands is generally discussed below, with reference to particular exemplified proligands. FIG. 42 summarizes the proligands synthesized and disclosed herein.

General Procedure for the Synthesis of Urea Proligands:

Urea proligands were prepared following a modified literature procedure³ in which the aniline (1 equiv) was dissolved in DCM and the solution was cooled to 0° C. Triphosgene (0.35 equiv) was added in one portion. The solution was stirred for five minutes after which N,N-diisopropylethylamine (2 equiv) was added and the cold bath removed. The solution was stirred for 1 hour and then piperidine (1 equiv) and a second portion of N,N-diisopropylethylamine (1 equiv) were added. The solution was stirred for an additional hour, and then diluted with 1M HCl. The organic phase was washed three times with 1M HCl dried over MgSO₄, filtered, and concentrated by rotary evaporation.

Synthesis of 3-(2,6-dimethylphenyl)-1,1-diphenylurea

Prepared following the general procedure outlined above. Recrystallization provided the desired compound as a white solid (1.2 g, Unoptimized Synthesis): ¹H NMR (CDCl₃, 300 MHz, 298 K): δ 7.42-7.38 (overlapping m, 8H, o-C₆H₅ and m-C₆H₅), 7.29-7.18 (m, 2H, p-C₆H₅), 7.05 (s, 3H, 2,6-Me₂C₆H₃), 5.79 (NH), 2.27 (s, 6H, CH₃) ppm. ¹³C NMR (CDCl₃, 75 MHz, 298 K): δ 153.94 (C═O), 142.72 (i-C₆H₅), 135.68 (o-C₆H₃), 134.56 (i-C₆H₃), 129.53 (m-C₆H₅), 128.12 (m-C₆H₃), 127.28 (o-C₆H₅), 126.85 (p-C₆H₅), 126.40 (p-C₆H₃), 18.62 (CH₃) ppm.

A ¹H NMR spectrum (300 MHz, CDCl₃, 298 K) of 3-(2,6-dimethylphenyl)-1,1-diphenylurea is shown in FIG. 1. A ¹³C NMR spectrum (75 MHz, CDCl₃, 298 K) of 3-(2,6-dimethylphenyl)-1,1-diphenylurea is shown in FIG. 2.

Synthesis of 3-(2,6-dimethylphenyl)-1-isopropyl-1-phenylurea

Prepared following the general procedure outlined above. Recrystallization provided the desired compound as a white solid (1.1 g, Unoptimized Synthesis): ¹H NMR (CDCl₃, 400 MHz, 298 K): δ 7.61-7.28 (overlapping m, 5H, o,m,p-C₆H₅), 6.99 (s, 3H, C₆H₃), 5.24 (NH), 4.96 (hept, ³J_(H—H)=6.5 Hz, 1H, CH(CH₃)₂), 2.19 (s, 6H, 2,6-(CH₃)₂C₆H₃), 1.14 (d, ³J_(H—H)=6.2 Hz, 6H, CH(CH₃)₂) ppm. ¹³C NMR (CDCl₃, 101 MHz, 298 K): 154.62 (C═O), 138.17 (i-C₆H₅), 135.71 (o-C₆H₃), 135.18 (i-C₆H₃), 131.21 (m-C₆H₃), 129.83 (o-C₆H₅), 128.66 (p-C₆H₅), 127.94 (m-C₆H₃), 126.38 (p-C₆H₃), 46.58 (CH(CH₃)₂), 21.65 (CH(CH₃)₃), 18.47 (2,6-(CH₃)₂C₆H₃) ppm.

A ¹H NMR spectrum (300 MHz, CDCl₃, 298 K) of 3-(2,6-dimethylphenyl)-1-isopropyl-1-phenylurea is shown in FIG. 3. A ¹³C NMR spectrum (75 MHz, CDCl₃, 298 K) of 3-(2,6-dimethylphenyl)-1-isopropyl-1-phenylurea.

Cyclic Ureate Ligands

Synthesis and Characterization of Cyclic Ureate Proligands

Synthesis of 1-cyclohexylimidazolidin-2-one (^(Cy)LH)

-   -   A solution 2-chloroethyl isocyanate (1.11 g, 10.5 mmol) in THF         (50 mL) was added dropwise to a stirring solution of         cyclohexylamine (0.99 g, 10 mmol) in THF (20 mL) at room         temperature. The resulting reaction mixture was treated with NaH         (0.24 g, 10 mmol) under an inert atmosphere and stirred at room         temperature overnight under an inert atmosphere. The mixture was         treated with saturated NH₄Cl (100 mL) and EtOAc (200 mL). The         organic layer was separated and the aqueous layer was extracted         with EtOAc (3×50 mL). The combined organic fractions were dried         over Na₂SO₄ and concentrated under vacuum to form a colorless         suspension in EtOAc. The reaction mixture was filtered and the         resulting solid was dried to form the desired product. Yield         (0.44 g, 27%). ¹H NMR (CDCl₃, 300 MHz, 298 K): δ 5.41 (br s, 1H,         NH), 3.77-3.58 (m, 1H, NCH), 3.43 (s, 4H, CH₂CH₂NH), 1.92-1.52         (m, 11H, HNCH₂) ppm. ¹³C NMR (CDCl₃, 75 MHz, 298 K): δ 162.52         (C═O), 40.71 (^(tBu)NCH₂), 51.15 (CH), 38.76 (HNCH₂), 30.39         (^(Cy)CH₂), 25.64 (^(Cy)CH₂) ppm. HRMS (ESI): m/z calcd for         C₉H₁₆N₂ONa [M+Na⁺]: 191.1160. Found: 191.1159.

FIG. 22 is a ¹H NMR spectrum (300 MHz, CDCl₃, 298 K) of 1-cyclohexylimidazolidin-2-one (^(cy)LH). FIG. 23 is a ¹³C NMR spectrum (100 MHz, CDCl₃, 298 K) of 1-cyclohexylimidazolidin-2-one (^(Cy)LH).

Synthesis of 1-phenylimidazolidin-2-one (^(Ph)LH)

A solution 2-chloroethyl isocyanate (1.05 g, 10 mmol) in THF (50 mL) was added dropwise to a stirring solution of phenylamine (0.93 g, 10 mmol) in THF (20 mL) at −20° C. The solution was brought to room temperature overnight. The resulting reaction mixture was treated with NaH (0.24 g, 10 mmol) under an inert atmosphere and stirred at room temperature overnight. The mixture was treated with saturated NH₄Cl (100 mL) and EtOAc (200 mL). The organic layer was separated and the aqueous layer was extracted with EtOAc (3×50 mL). The combined organic fractions were dried over Na₂SO₄ and concentrated under vacuum to form a colorless suspension in EtOAc. The reaction mixture was filtered and the resulting solid was dried to form the desired product. Yield (0.42 g, 26%). ¹H NMR (CDCl₃, 300 MHz, 298 K): δ 7.58 (d, 2H, J_(H—H)=8.2 Hz, m-C₆H₅), 7.38-7.29 (m, 2H, o-C₆H₅), 7.05 (t, 2H, J_(H—H)=7.2 Hz, p-C₆H₅), 4.00-3.84 (m, 2H, ^(Ph)NCH₂), 3.65-3.48 (m, 2H, HNCH₂) ppm. ¹³C NMR (CDCl₃, 75 MHz, 298 K): δ 160.27 (C═O), 140.18 (C₆H₅), 128.92 (C₆H₅), 122.83 (C₆H₅), 118.09 (C₆H₅), 45.49 (^(Ph)NCH₂), 37.70 (HNCH₂) ppm. HRMS (ESI): m/z calcd for C₉H₁₀N₂ONa [M+Na⁺]: 185.0691. Found: 185.0691.

FIG. 24 is a ¹H NMR spectrum (300 MHz, CDCl₃, 298 K) of 1-phenylimidazolidin-2-one (^(Ph)LH). FIG. 25 is a ¹H NMR spectrum (75 MHz, CDCl₃, 298 K) of 1-phenylimidazolidin-2-one (^(Ph)LH).

Synthesis of 1-(tert-butyl)imidazolidin-2-one (^(tBu)LH)

A solution 2-chloroethyl isocyanate (6.80 g, 64 mmol) in THF (50 mL) was added dropwise to a stirring solution of tertbutylamine (4.28 g, 58.5 mmol) in THF (20 mL) at −20° C. The solution was brought to room temperature overnight. The resulting reaction mixture was treated with NaH (6.8 g, 283 mmol) under an inert atmosphere and heated at 65° C. overnight under an inert atmosphere. The mixture was brought to dryness and treated with saturated NH₄Cl (100 mL) and EtOAc (200 mL). The organic layer was separated and the aqueous layer was extracted with EtOAc (3×50 mL). The combined organic fractions were dried over Na₂SO₄ and brought to dryness under vacuum forming a yellow oil. Hexanes (5 mL) were then added resulting with the formation of a solid at the bottom of the round bottom flask. The mother liquor was removed by filtration. This process was repeated 3 more times and the combined hexane solutions (fraction 1) were stored at −30° C. overnight, while the solid (fraction 2) was also kept. Storing the combined hexane solutions (fraction 1) at low temperatures resulted in the formation of colorless crystals that were later filtered and dried in vacuo to afford 350 mg of pure product. The solid from fraction 2 was sublimed at 100° C. under vacuum to afford a waxy solid on the cold finger. The resulting waxy solid was washed with hexanes (2×4 mL) to afford 770 mg of pure product. Total yield: 1.12 g (13%). ¹H NMR (CDCl₃, 300 MHz, 298 K): δ 4.37 (br s, 1H, NH), 3.49-3.40 (m, 2H, ^(tBu)NCH₂), 3.33-3.23 (m, 2H, HNCH₂), 1.36 (s, 9H, C(CH₃)₃) ppm. ¹³C NMR (CDCl₃, 75 MHz, 298 K): δ 163.15 (C═O), 52.96 (C(CH₃)₃), 43.73 (^(TbU)NCh₂), 38.13 (HNCH₂), 27.67 (C(CH₃)₃) ppm. HRMS (ESI): m/z calcd for C₇H₁₄N₂O [M+Na⁺]: 165.10039. Found: 165.1001. Anal. Calcd. for C₇H₁₄N₂O: C, 59.12; H, 9.92; N, 19.70; Found: C, 59.12; H, 10.29; N, 19.71.

FIG. 26 is a ¹H NMR spectrum (300 MHz, CDCl₃, 298 K) of 1-(tert-butyl)imidazolidin-2-one (^(tBu)LH). FIG. 27 is a ¹³C NMR spectrum (75 MHz, CDCl₃, 298 K) of 1-(tert-butyl)imidazolidin-2-one (^(tBu)LH).

Synthesis of Cyclic Ureate Ligand Salts

General Procedure for the Synthesis of Ligand Salts ^(x)LH (X=Me,Cy, pH, ^(t)Bu):

NaN(SiMe₃)₂ (1 equiv.) and the corresponding proteoligand (1 equiv.) were mixed in toluene (˜5 mL) and stirred overnight at room temperature. The volatiles were then removed at low pressure and the resulting solid was thoroughly stripped with hexanes (3×5 mL) and dried to give the sodium salt in moderate to quantitative yields as a colorless powder. The resulting ligand salts were used directly without further purification via storage in a glove box. Except in the case of ^(Dipp)LH, NMR characterization was precluded due to poor solubility in common NMR solvents (e.g. d₆-benzene or d₈-toluene).

Synthesis of sodium 3-methyl-2-oxoimidazolidin-1-ide (^(Me)L⁻Na⁺)

Prepared following the general procedure outlined above: ^(Me)LH (197 mg, 1.97 mmol) and NaN(SiMe₃)₂ (361 mg, 1.97 mmol). Yield (163 mg, 68%).

Synthesis of sodium 3-cyclohexyl-2-oxoimidazolidin-1-ide (^(Cy)L⁻Na⁺)

Prepared following the general procedure outlined above: ^(cy)LH (100 mg, 0.59 mmol) and NaN(SiMe₃)₂ (109 mg, 0.59 mmol). Yield (107 mg, 95%).

Synthesis of sodium 2-oxo-3-phenylimidazolidin-1-ide (^(Ph)L⁻Na+)

Prepared following the general procedure outlined above: ^(Ph)LH (150 mg, 0.93 mmol) and NaN(SiMe₃)₂ (170 mg, 0.93 mmol). Yield (140 mg, 82%).

Synthesis of sodium 3-(tert-butyl)-2-oxoimidazolidin-1-ide (^(tBu)L⁻Na⁺)

Prepared following the general procedure outlined above: ^(tBu)L⁻Na⁺ (230 mg, 1.62 mmol) and NaN(SiMe₃)₂ (297 g, 1.62 mmol). Yield (265 mg, 99%).

Acyclic Ureate Ligands Synthesis and Characterization of Proteoligands

General procedure for the synthesis of urea based proteoligands: Prepared following a modified literature procedure in which a chosen primary amine (1 equiv.) was dissolved in dichloromethane and the solution was cooled to 0° C. Triphosgene (0.35 equiv.) was added in portions as a solid. The solution was stirred for five minutes after which N,N-diisopropylethylamine DIPEA (3 equiv.) was added and the cold bath removed. The solution was stirred for 1 hour and then the appropriate amine (1 equiv.) and a second portion of DIPEA (1 equiv.) was added. The solution was stirred for an additional hour, and then diluted with 3M HCl. The organic phase was washed three times with 1M HCl dried over MgSO₄, filtered, and concentrated by rotary evaporation to give the crude product.

Synthesis of 3-(2,6-dimethylphenyl)-1-methyl-1-(1-phenylethyl)urea

Prepared following the general procedure outlined above: 2,6-dimethylaniline (2.25 g, 18.5 mmol), triphosgene (1.81 g, 6.10 mmol), DIPEA (7.2 g, 55.5 mmol), N-methyl-1-phenylethan-1-amine (2.5 g, 18.5 mmol). Recrystallization from a concentrated ethyl acetate solution provided the desired compound as a white solid (3.48 g, 66.9%): ¹H NMR (CDCl₃, 300 MHz, 298 K): δ 7.41-7.26 (overlapping m, 5H, o-C₆H₅ m-C₆H₅, and p-C₆H₅), 7.04 (s, 3H, m-C₆H₅, and p-C₆H₅), 5.86 (br s, 1H, NH), 5.64-5.57 (q, 1H, CHCH₃), 2.79 (s, 3H, CH₃), 2.19 (s, 6H, 2,6-(CH₃)₂C₆H₃) ppm. ¹³C NMR (CDCl₃, 75 MHz, 298 K): δ 156.31 (C═O), 141.79, 135.58, 135.33, 128.64, 128.07, 127.28, 126.88, 126.34, 52.80, 29.53, 18.43, 17.02 ppm. HRMS (ESI): m/z calcd for C₁₈H₂₃N₂O [M+H⁺]: 283.1810. Found: 283.1809.

FIG. 33 is a ¹H NMR spectrum (400 MHz, CDCl₃, 298 K) of 3-(2,6-dimethylphenyl)-1-methyl-1-(1-phenylethyl)urea. FIG. 34 is a ¹³C NMR spectrum (100 MHz, benzene-d₆, 298 K) of 3-(2,6-dimethylphenyl)-1-methyl-1-(1-phenylethyl)urea.

Synthesis of 3-(2,6-dimethylphenyl)-1-isopropyl-1-phenylurea

Prepared following the general procedure outlined above: 2,6-dimethylaniline (1.5 g, 20.5 mmol), triphosgene (2.02 g, 7.41 mmol), DIPEA (7.95 g, 61.5 mmol), N-isopropylaniline (2.5 g, 20.5 mmol). Recrystallization from a concentrated ethyl acetate solution provided the desired compound as a white solid (3.20 g, 65%): ¹H NMR (CDCl₃, 400 MHz, 298 K): δ 7.05 (s, 3H, o,m,p-C₆H₅), 5.69 (br s, 1H, NH), 4.56-4.49 (m, 1H, CH(CH₃)₂), 2.86 (s, 3H, CH₃), 2.24 (s, 6H, 2,6-(CH₃)₂C₆H₃), 1.17 (d, J_(H—H)=1.7 Hz, 6H, CH(CH₃)₂) ppm. ¹³C NMR (CDCl₃, 101 MHz, 298 K): δ 156.00 (C═O), 135.70, 135.57, 128.20, 126.40, 45.89, 27.45, 20.21, 18.56 ppm. HRMS (ESI): m/z calcd for C₁₃H₂₁N₂O [M+H⁺]: 221.1654. Found: 221.1656.

FIG. 35 is a ¹H NMR spectrum (400 MHz, CDCl₃, 298 K) of 3-(2,6-dimethylphenyl)-1-isopropyl-1-phenylurea. FIG. 36 is a ¹³C NMR spectrum (100 MHz, benzene-d₆, 298 K) of 3-(2,6-dimethylphenyl)-1-isopropyl-1-phenylurea.

Synthesis of 1-benzhydryl-3-(2,6-dimethylphenyl)-1-methylurea

Prepared following the general procedure outlined above: 2,6-dimethylaniline (307 mg, 2.53 mmol), triphosgene (250.2 mg, 0.843 mmol), DIPEA (981 mg, 7.59 mmol), N-methyl-1,1-diphenylmethanamine (500 mg, 2.53 mmol). Recrystallization from a concentrated ethyl acetate solution provided the desired compound as a white solid (750 mg, 86%): ¹H NMR (CDCl₃, 400 MHz, 298 K): δ 7.41-7.27 (overlapping m, 10H, o,m,p-C₆H₅), 7.04 (s, 3H, m,p-C₆H₅), 6.70 (s, 1H, NHCH), 5.78 (br s, 1H, NH), 2.88 (s, 3H, CH₃), 2.16 (s, 6H, 2,6-(CH₃)₂C₆H₃) ppm. ¹³C NMR (CDCl₃, 101 MHz, 298 K): δ 156.57 (C═O), 139.66, 135.47, 135.30, 128.80, 128.77, 128.25, 127.80, 126.49, 63.30, 32.05, 28.48 ppm. HRMS (ESI): m/z calcd for C₂₃H₂₅N₂O [M+H⁺]: 345.1967 Found: 345.1964.

FIG. 37 is a ¹H NMR spectrum (400 MHz, CDCl₃, 298 K) of 1-benzhydryl-3-(2,6-dimethylphenyl)-1-methylurea. FIG. 38 is a ¹³C NMR spectrum (100 MHz, CDCl₃, 298 K) of 1-benzhydryl-3-(2,6-dimethylphenyl)-1-methylurea.

Synthesis of 3-(2,6-diisopropylphenyl)-1-methyl-1-(1-phenylethyl)urea

Prepared following the general procedure outlined above: 2,6-dimethylaniline (1.32 g, 7.40 mmol), triphosgene (724 mg, 2.44 mmol), DIPEA (2.87 g, 22.2 mmol), N-methyl-1,1-diphenylmethanamine (1.0 g, 7.40 mmol). Recrystallization from a concentrated ethyl acetate solution provided the desired compound as a white solid (1.81 g, 72.3%): ¹H NMR (CDCl₃, 400 MHz, 298 K): δ 7.51-7.50 (overlapping m, 4H), 7.45-7.39 (overlapping m, 2H), 7.37-7.35 (m, 1H), 7.28 (m, 1H), 5.78-5.72 (overlapping m, 2H), 3.22-3.12 (m, 2H, CH(CH₃)₂), 3.00 (s, 3H, CH₃), 1.72 (s, 3H, CH₃), 1.31 (s, 12H, CH(CH₃)₂) ppm. ¹³C NMR (CDCl₃, 101 MHz, 298 K): δ 157.22 (C═O), 146.52, 142.12, 132.80, 128.73, 127.63, 127.41, 126.95, 123.36, 52.99, 29.82, 28.79, 23.81 ppm. HRMS (ESI): m/z calcd for C₂₂H₃₁N₂O [M+H⁺]: 339.2437. Found: 339.2444.

FIG. 39 is a ¹H NMR spectrum (400 MHz, CDCl₃, 298 K) of 3-(2,6-diisopropylphenyl)-1-methyl-1-(1-phenylethyl)urea. FIG. 40 is a ¹³C NMR spectrum (100 MHz, CDCl₃, 298 K) of 3-(2,6-diisopropylphenyl)-1-methyl-1-(1-phenylethyl)urea.

Synthesis of Ta(CH₂SiMe₃)₃Br₂

A solution of Zn(CH₂SiMe₃)₂ (0.64 g, 2.67 mmol) in hexanes (20 mL) was added to a suspension of TaBr₅ (1.00 g, 1.72 mmol) in hexanes (10 mL). The reaction mixture was stirred at room temperature overnight forming a colorless precipitate. The following day, the solution was filtered and concentrated in vacuo to afford the formation of the title product as yellow powder. Yield (0.73 g, 71%). ¹H NMR (toluene-d₈, 300 MHz, 298 K): δ 2.11 (s, 6H, CH₂), 0.29 (s, 27H, SiCH₃) ppm.

3.3 Ligand Salts

General procedure for the synthesis of ligand salts NaN(SiMe₃)₂ (1 equiv.) was added in portions to a suspension of the corresponding proteo-ligand (1 equiv.) in Et₂O (˜10 mL) and stirred overnight at room temperature. The volatiles were then removed at low pressure and the resulting solid was thoroughly washed with hexanes (3×5 mL) and dried to give the sodium salt as a colorless powder. Salts were used directly without further characterization.

Synthesis and Characterization of Tantalum Based Ureate Complexes

FIG. 28 is a ¹H NMR spectrum (300 MHz, toluene-d₈, 298 K) of Ta(CH₂SiMe₃)₃Br₂.

Synthesis of ^(tBu)LTa(CH₂SiMe₃)₃Cl

A suspension of ^(tBu)L⁻Na⁺ (71 mg, 0.43 mmol) in toluene (3 mL) was added dropwise at room temperature to a solution of Ta(CH₂SiMe₃)Cl₂ (200 mg, 0.39 mmol) in toluene (3 mL). The reaction mixture was stirred for 30 min. The volatiles were then removed in vacuo and the title complex was extracted with hexanes (3×5 mL) and filtered over celite. The resulting organic solution was concentrated to approx. 3 mL and stored in a freezer at −30° C. A large crop of crystals were formed overnight which were further dried affording the title compound as pale yellow crystals. Yield (150 mg, 62%). ¹H NMR (benzene-d₆, 300 MHz, 298 K): δ 3.36-3.23 (m, 2H, NCH₂), 2.75-2.62 (m, 2H, NCH₂), 1.57 (s, 6H, CH₂SiMe₃), 1.06 (s, 9H, NC(CH₃)₃, 0.36 (s, 27H, SiCH₃) ppm. ¹³C NMR (benzene-d₆, 75 MHz, 298 K): δ 171.36 (C═O), 90.19 (CH₂SiMe₃), 53.68 (NC(CH₃)₃), 45.38 (NCH₂), 44.41 (NCH₂), 27.96 (NC(CH₃)₃), 2.79 (SiCH₃) ppm. LRMS (ESI): m/z: 531 (M-CH₂SiMe₃-H⁺), 443 (M-2CH₂SiMe₃-2H⁺). Anal. Calcd. for C₁₉H₄₇ClN₂OSi₃Ta: C, 36.79; H, 7.64; N, 4.52; Found: C, 36.44; H, 7.69; N, 4.59.

FIG. 29 is a ¹H NMR spectrum (300 MHz, benzene-d₆, 298 K) of ^(tBu)LTa(CH₂SiMe₃)₃Cl. FIG. 30 is a ¹³C NMR spectrum (75 MHz, benzene-d₆, 298 K) of ^(tBu)LTa(CH₂SiMe₃)₃Cl.

Synthesis of ^(tBu)LTa(CH₂SiMe₃)₃Br

A suspension of ^(tBu)L⁻Na⁺ (30 mg, 0.19 mmol) in toluene (3 mL) was added dropwise at room temperature to a solution of Ta(CH₂SiMe₃)Cl₂ (106 mg, 0.18 mmol) in toluene (3 mL). The reaction mixture was stirred for 30 min. The volatiles were then removed in vacuo and the title complex was extracted with hexanes (3×5 mL) and filtered over celite. The resulting organic solution was concentrated to approx. 3 mL and stored in a freezer at −30° C. A large crop of crystals were formed overnight which were further dried affording the title compound as pale yellow crystals. Yield (35 mg, 30%). ¹H NMR (benzene-d₆, 400 MHz, 298 K): δ 3.31-3.24 (m, 2H, NCH₂), 2.72-2.65 (m, 2H, NCH₂), 1.62 (s, 6H, CH₂SiMe₃), 1.05 (s, 9H, NC(CH₃)₃, 0.37 (s, 27H, SiCH₃) ppm. ¹³C NMR (benzene-d₆, 75 MHz, 298 K): δ 171.18 (C═O), 94.33 (CH₂SiMe₃), 53.78 (NC(CH₃)₃), 45.34 (NCH₂), 44.16 (NCH₂), 27.96 (NC(CH₃)₃), 2.91 (SiCH₃) ppm.

FIG. 31 is a ¹H NMR spectrum (400 MHz, benzene-d₆, 298 K) of ^(tBu)LTa(CH₂SiMe₃)₃Br. FIG. 32 is a ¹³C NMR spectrum (100 MHz, benzene-d₆, 298 K) of ^(tBu)LTa(CH₂SiMe₃)₃Br.

Synthesis and Characterization of Tantalum Based Ureate Complexes Synthesis of LTa(CH₂SiMe₃)₃Cl

A suspension of L⁻Na⁺ (206 mg, 0.81 mmol) in toluene (5 mL) was added dropwise at room temperature to a solution of Ta(CH₂SiMe₃)Cl₂ (378 mg, 0.736 mmol) in toluene (6 mL). The reaction mixture was stirred for 30 min. The volatiles were then removed in vacuo and the title complex was extracted with hexanes (3×5 mL) and filtered over celite. The resulting organic solution was concentrated to approx. 3 mL and stored in a freezer at −30° C. Over a week period, a large amount of solid precipitated. The mixture was then filtered and the resulting solid was dried in vacuo to form the desired complex. Yield (370 mg, 71%). ¹H NMR (benzene-d₆, 300 MHz, 298 K): δ 6.92-6.80 (m, 3H, C₆H₃), 3.52-3.85 (m, 2H, CH₂), 2.21 (s, 6H, CH₂SiMe₃), 1.41 (s, 6H, CH₃), 0.39 (s, 27H, SiCH₃) ppm.

FIG. 41 is a ¹H NMR spectrum (300 MHz, benzene-d₆, 298 K) of LTa(CH₂SiMe₃)₃Cl.

3.4 Hydroaminoalkylation Reaction:

General Procedure for Hydroaminoalkylation Reaction:

Solid tantalum precursor (0.0025 mmol) was weighed into a vial, followed by addition of the chosen ligand salt (0.025 mmol) d₈-toluene (0.3 g) was added, and the resultant mixture was left for 15 minutes. A chosen amine substrate was then added (0.5 mmol), followed by the alkene (0.5 mmol). The resultant reaction mixture was transferred into a J. Young NMR tube and the vial was rinsed with an additional 0.2 g of d₈-toluene. An initial ¹H NMR spectrum was recorded and the sample was added to a pre-heated oil bath. All conversion values were determined by ¹H NMR spectroscopy. After removal of all reaction solvent, pentane was added to the reaction mixture and a white precipitate was formed instantaneously. Residual tantalum salts and proteo-ligands were then removed by filtering the pentane solution at −80° C. Unreacted amine or alkene starting materials were removed at 40° C. under low pressure. In all cases, ¹H NMR spectroscopy still showed the presence of proteo-ligands in low amounts (2-4%), which can be entirely removed by column chromatography. N-(2-propylhexyl)aniline and N-(2-ethylpentyl)aniline showed signs of decomposition while heated under vacuum, and therefore must be purified by column chromatography.

N-(2-methyloctyl)aniline:

N-methylaniline (54 mg, 0.5 mmol), 1-octene (0.056 g, 0.5 mmol), Ta(CH₂SiMe₃)₃Cl₂ (13 mg, 0.025 mmol), L4 (8 mg, 0.025 mmol). Reaction time: 2 h. Yield 88%. ¹H NMR (CDCl₃, 300 MHz, 298 K): δ 7.24-7.16 (m, 2H, bum-C₆H₅), 6.75-6.67 (m, 1H, p-C₆H₅), 6.67-6.60 (m, 2H, o-C₆H₅), 3.69 (br s, 1H, NH), 3.08 (dd, J_(H—H)=12.8, 5.8 Hz, 1H, NC(H)H), 2.91 (dd, J_(H—H)=12.2, 7.3 Hz, 1H, NC(H)H), 1.86-1.68 (m, 1H, 1.53-1.14 (overlapping m, 10H, CH₂), 1.00 (d, J_(H—H)=6.6 Hz, 3H, CHCH₃), 0.97-0.89 (t, J_(H—H)=6.1 Hz, 3H, CH₂CH₃) ppm. The chemical shifts for the title compound match those reported by Hartwig et al.

N-(cyclooctylmethyl)aniline

N-methylaniline (54 mg, 0.5 mmol), cyclooctene (55 mg, 0.5 mmol), Ta(CH₂SiMe₃)₃Cl₂ (13 mg, 0.025 mmol), L5 (8 mg, 0.025 mmol). Reaction time: 6 h. Yield 83%. ¹H NMR (CDCl₃, 300 MHz, 298 K): δ 7.20 (dd, J_(H—H)=8.5, 7.4 Hz, 2H, m-C₆H₅), 6.70 (t, J_(H—H)=6.7 Hz, 1H, p-C₆H₅), 6.62 (dd, J_(H—H)=8.5, 0.9 Hz, 2H, o-C₆H₅), 3.71 (br s, 1H, NH), 2.08 (d, J_(H—H)=6.8 Hz, NCH₂), 1.92-1.27 (overlapping m, 13H, CH₂ and CH) ppm.

4-methoxy-N-(2-methyloctyl)aniline

4-methoxy-N-methylaniline (96 mg, 0.5 mmol), 1-octene (0.056 g, 0.5 mmol), Ta(CH₂SiMe₃)₃Cl₂ (13 mg, 0.025 mmol), L4 (8 mg, 0.025 mmol). Reaction time: 2 h. Yield 77%. ¹H NMR (CDCl₃, 300 MHz, 298 K): δ 6.84-6.74 (m, 2H, m-C₆H₄), 6.63-6.55 (m, 2H, o-C₆H₄), 3.76 (s, 3H, OCH₃), 3.38 (br s, 1H, NH), 3.02 (dd, J_(H—H)=5.8, 12.1 Hz, 1H, NC(H)H), 3.02 (dd, J_(H—H)=7.8, 12.1 Hz, 1H, NC(H)H), 1.82-1.64 (m, 1H, CH), 1.55-1.05 (m, 10H, CH₂), 0.98 (d, J_(H—H)=6.6 Hz, 3H, CHCH₃), 0.91 (t, J_(H—H)=6.7 Hz, 3H, CH₂CH₃) ppm. The chemical shifts for the title compound match those previously reported in the literature.

4-bromo-N-(2-methyloctyl)aniline

4-bromo-N-methylaniline (93 mg, 0.5 mmol), 1-octene (0.056 g, 0.5 mmol), Ta(CH₂SiMe₃)₃Cl₂ (13 mg, 0.025 mmol), L4 (8 mg, 0.025 mmol). Reaction time: 2 h. Yield 86%. ¹H NMR (CDCl₃, 300 MHz, 298 K): δ 7.23 (d, J_(H—H)=8.7 Hz, 2H, m-C₆H₄), 6.48 (d, J_(H—H)=8.9 Hz, 2H, o-C₆H₄), 3.92 (br s, 1H, NH), 3.01 (dd, J_(H—H)=5.9, 12.2 Hz, 1H, NC(H)H), 2.84 (dd, J_(H—H)=7.1, 12.1 Hz, 1H, NC(H)H), 1.78-1.65 (m, 1H, CH), 1.51-1.08 (m, 10H, CH₂), 0.96 (d, J_(H—H)=6.6 Hz, 3H, CHCH₃), 0.89 (t, J_(H—H)=6.9 Hz, 3H, CH₂CH₃) ppm. ¹³C NMR (CDCl₃, 75 MHz, 298 K): δ 148.51 (i-C₆H₄), 129.34 (m-C₆H₄), 117.24 (p-C₆H₄), 112.87 (o-C₆H₄), 48.11, 47.99, 37.45, 37.28, 36.79, 36.56, 29.68, 27.37, 27.00, 26.11, 25.95, 25.04, 14.94 (CH₃), 14.48 (CH₃) ppm.

FIG. 5 is a ¹H NMR spectrum (300 MHz, CDCl₃, 298 K) of 4-bromo-N-(2-methyloctyl)aniline. FIG. 6 is a ¹³C NMR spectrum (100 MHz, CDCl₃, 298 K) of 4-bromo-N-(2-methyloctyl)aniline.

4-bromo-N-(cyclooctylmethyl)aniline

4-bromo-N-methylaniline (93 mg, 0.5 mmol), cyclooctene (55 mg, 0.5 mmol), Ta(CH₂SiMe₃)₃Cl₂ (13 mg, 0.025 mmol), L5 (8 mg, 0.025 mmol). Reaction time: 6 h. Yield 95%. ¹H NMR (CDCl₃, 300 MHz, 298 K): δ 7.25 (d, J_(H—H)=8.8 Hz, m-C₆H₄), 6.47 (d, J_(H—H)=8.8 Hz, o-C₆H₄), 3.75 (br s, 1H, NH), 2.90 (d, J_(H—H)=6.8 Hz, NCH₂), 1.86-1.24 (overlapping m, 13H, CH and CH₂) ppm. ¹³C NMR (CDCl₃, 75 MHz, 298 K): δ 147.65 (i-C₆H₄), 131.95 (m-C₆H₄), 114.25 (o-C₆H₄), 108.40 (p-C₆H₄), 51.21 (NCH₂), 37.33 (CH₂), 30.67 (CH₂), 27.13 (CH₂), 26.41 (CH₂), 25.58 (CH₂) ppm.

FIG. 7 is a ¹H NMR spectrum (300 MHz, CDCl3, 298 K) of 4-bromo-N-(cyclooctylmethyl)aniline. FIG. 8 is a ¹³C NMR spectrum (100 MHz, CDCl3, 298 K) of 4-bromo-N-(cyclooctylmethyl)aniline.

4-chloro-N-(2-methyloctyl)aniline

4-chloro-N-methylaniline (71 mg, 0.5 mmol), 1-octene (0.056 g, 0.5 mmol), Ta(CH₂SiMe₃)₃Cl₂ (13 mg, 0.025 mmol), L4 (8 mg, 0.025 mmol). Reaction time: 2 h. Yield 90%. ¹H NMR (CDCl₃, 300 MHz, 298 K): δ 7.12 (d, J_(H—H)=8.8 Hz, 2H, m-C₆H₅), 6.52 (d, J_(H—H)=8.8 Hz, 2H, o-C₆H₅), 3.78 (br s, 1H, NH), 3.02 (dd, J_(H—H)=5.9, 12.2 Hz, 1H, NC(H)H), 2.86 (dd, J_(H—H)=7.2, 12.2 Hz, 1H, NC(H)H), 1.82-1.65 (m, 1H, 1.51-1.09 (m, 10H, CH₂), 0.97 (d, J_(H—H)=6.6 Hz, 3H, CHCH₃), 0.91 (t, J_(H—H)=6.8 Hz, 3H, CH₂CH₃) ppm. The chemical shifts for the title compound match those previously reported in the literature.

4-chloro-N-(cyclooctylmethyl)aniline

4-chloro-N-methylaniline (71 mg, 0.5 mmol), cyclooctene (55 mg, 0.5 mmol), Ta(CH₂SiMe₃)₃Cl₂ (13 mg, 0.025 mmol), L5 (8 mg, 0.025 mmol). Reaction time: 6 h. Yield 93%. ¹H NMR (CDCl₃, 300 MHz, 298 K): δ 7.10 (d, J_(H—H)=8.8 Hz, m-C₆H₄), 6.51 (d, J_(H—H)=8.8 Hz, o-C₆H₄), 3.71 (br s, 1H, NH), 2.90 (d, J_(H—H)=6.8 Hz, NCH₂), 1.87-1.21 (overlapping m, 13H, CH and CH₂). ppm. ¹³C NMR (CDCl₃, 75 MHz, 298 K): δ 147.29 (i-C₆H₄), 129.10 (m-C₆H₄), 121.41 (p-C₆H₄), 113.73 (o-C₆H₄), 51.32 (NCH₂), 37.38 (CH₂), 30.70 (CH₂), 27.14 (CH₂), 26.43 (CH₂), 25.59 (CH₂) ppm.

FIG. 9 is a ¹H NMR spectrum (300 MHz, CDCl3, 298 K) of 4-chloro-N-(cyclooctylmethyl)aniline. FIG. 10 is a ¹³C NMR spectrum (100 MHz, CDCl₃, 298 K) of 4-chloro-N-(cyclooctylmethyl)aniline.

4-fluoro-N-(2-methyloctyl)aniline

4-fluoro-N-methylaniline (63 mg, 0.5 mmol), 1-octene (0.056 g, 0.5 mmol), Ta(CH₂SiMe₃)₃Cl₂ (13 mg, 0.025 mmol), L4 (8 mg, 0.025 mmol). Reaction time: 2 h. Yield 88%. ¹H NMR (CDCl₃, 300 MHz, 298 K): δ 6.89 (t, J_(H—H)=8.8 Hz, 2H, m-C₆H₅), 6.59-6.50 (m, 2H, o-C₆H₅), 3.57 (br s, 1H, NH), 3.02 (dd, J_(H—H)=5.9, 12.1 Hz, 1H, NC(H)H), 2.85 (dd, J_(H—H)=7.2, 12.0 Hz, 1H, NC(H)H), 1.82-1.65 (m, 1H, 1.51-1.11 (m, 10H, CH₂), 0.98 (d, J_(H—H)=6.7 Hz, 3H, CHCH₃), 0.91 (t, JH—H=6.9 Hz, 3H, CH₂CH₃) ppm.

N-(cyclooctylmethyl)-4-fluoroaniline

4-fluoro-N-methylaniline (63 mg, 0.5 mmol), cyclooctene (55 mg, 0.5 mmol), Ta(CH₂SiMe₃)₃Cl₂ (13 mg, 0.025 mmol), L5 (8 mg, 0.025 mmol). Reaction time: 6 h. Yield 88%. ¹H NMR (CDCl₃, 300 MHz, 298 K): δ 6.89 (t, J_(H—H)=8.7 Hz, 2H, m-C₆H₄), 6.57-6.49 (m, 2H, o-C₆H₄), 3.58 (br s, 1H, NH), 2.90 (d, J_(H—H)=6.7 Hz, 2H, NCH₂), 1.88-1.22 (overlapping m, 13H, CH and CH₂) ppm. ¹³C NMR (CDCl₃, 100 MHz, 298 K): δ 155.68 (d, J_(C—F)=234.2 Hz, p-C₆H₄), 145.05 (i-C₆H₄), 115.66 (d, J_(C—F)=22.2 Hz, m-C₆H₄), 113.49 (d, J_(C—F)=7.3 Hz, o-C₆H₄), 51.99 (NCH₂), 37.41 (CH₂), 30.72 (CH₂), 27.15 (CH₂), 26.43 (CH₂), 25.60 (CH₂) ppm. ¹⁹F NMR (CDCl₃, 282.4 MHz, 298 K): δ −129.00 (tt, J_(H—F)=4.5 Hz, 1F, C₆H₄F) ppm.

FIG. 11 is a ¹H NMR spectrum (300 MHz, CDCl3, 298 K) of N-(cyclooctylmethyl)-4-fluoroaniline. FIG. 12 is a ¹³C NMR spectrum (75 MHz, CDCl3, 298 K) of N-(cyclooctylmethyl)-4-fluoroaniline

N-(2-methyloctyl)-4-(trifluoromethoxy)aniline

N-methyl-4-(trifluoromethoxy)aniline (96 mg, 0.5 mmol), 1-octene (0.056 g, 0.5 mmol), Ta(CH₂SiMe₃)₃Cl₂ (13 mg, 0.025 mmol), L4 (8 mg, 0.025 mmol). Reaction time: 3 h. Yield 92%. ¹H NMR (CDCl₃, 300 MHz, 298 K): δ 7.03 (d, J_(H—H)=8.2 Hz, 2H, m-C₆H₄), 6.59-6.50 (m, 2H, o-C₆H₄), 3.80 (br s, 1H, NH), 3.03 (dd, J_(H—H)=5.9, 12.2 Hz, 1H, NC(H)H), 2.85 (dd, J_(H—H)=7.3, 12.2 Hz, 1H, NC(H)H), 1.82-1.64 (m, 1H, 1.51-1.09 (m, 10H, CH₂), 0.97 (d, J_(H—H)=6.7 Hz, 3H, CHCH₃), 0.90 (t, J_(H—H)=6.9 Hz, 3H, CH₂CH₃) ppm. ¹³C NMR (CDCl₃, 300 MHz, 298 K): δ 147.51 (i-C₆H₅), 122.53 (C₆H₅), 112.89 (C₆H₅), 50.67 (NCH₂), 34.90, 33.02, 32.00, 29.73, 27.07, 22.81, 18.17 (CH₃), 14.23 (CH₃) ppm. ¹⁹F NMR (CDCl₃, 282.4 MHz, 298 K): δ −58.81 (s, 3F, CF₃) ppm.

FIG. 13 is a ¹H NMR spectrum (300 MHz, CDCl3, 298 K) of N-(2-methyloctyl)-4-(trifluoromethoxy)aniline. FIG. 14 is a ¹³C NMR spectrum (75 MHz, CDCl3, 298 K) of N-(2-methyloctyl)-4-(trifluoromethoxy)aniline.

N-(cyclooctylmethyl)-4-(trifluoromethoxy)aniline

N-methyl-4-(trifluoromethoxy)aniline (96 mg, 0.5 mmol), cyclooctene (55 mg, 0.5 mmol), Ta(CH₂SiMe₃)₃Cl₂ (13 mg, 0.025 mmol), L5 (8 mg, 0.025 mmol). Reaction time: 6 h. Yield 85%. ¹H NMR (CDCl₃, 300 MHz, 298 K): δ 7.03 (d, J_(H—H)=9.0 Hz, 2H, m-C₆H₄), 6.59-6.50 (m, 2H, o-C₆H₄), 3.77 (br s, 1H, NH), 0.2.92 (d, J_(H—H)=6.5 Hz, 1H, NCH₂), 1.89-1.21 (overlapping m, 13H, CH and CH₂) ppm. ¹³C NMR (CDCl₃, 75 MHz, 298 K): δ 147.55 (i-C₆H₄), 122.51 (C₆H₄), 112.81 (C₆H₄), 51.43 (NCH₂), 37.48, 30.73, 27.17, 26.44, 25.61 ppm. ¹⁹F NMR (CDCl₃, 282.4 MHz, 298 K): δ −58.79 (s, 3F, CF₃) ppm.

FIG. 15 is a ¹H NMR spectrum (300 MHz, CDCl3, 298 K) of N-(cyclooctylmethyl)-4-(trifluoromethoxy)aniline. FIG. 16 is a ¹³C NMR spectrum (75 MHz, CDCl3, 298 K) of N-(cyclooctylmethyl)-4-(trifluoromethoxy)aniline.

N-(2-methyloctyl)benzo[d][1,3]dioxol-5-amine

N-methylbenzo[d][1,3]dioxol-5-amine (76 mg, 0.5 mmol), 1-octene (0.056 g, 0.5 mmol), Ta(CH₂SiMe₃)₃Cl₂ (13 mg, 0.025 mmol), L4 (8 mg, 0.025 mmol). Reaction time: 2 h. Yield 85%. ¹H NMR (CDCl₃, 300 MHz, 298 K): δ 6.66 (d, J_(H—H)=8.3 Hz, 2H, m-C₆H₃), 6.25 (d, J_(H—H)=8.3 Hz, 1H, o-C₆H₃), 6.04 (dd, J_(H—H)=2.3, 8.3 Hz, 1H, o-C₆H₃), 5.85 (s, 2H, OCH₂), 3.48 (br s, 1H, NH), 2.99 (dd, J_(H—H)=5.9, 12.0 Hz, 1H, NC(H)H), 2.84 (dd, J_(H—H)=5.0, 12.2 Hz, 1H, NC(H)H), 1.81-1.62 (m, 1H, 1.50-1.08 (m, 10H, CH₂), 0.97 (d, J_(H—H)=6.7 Hz, 3H, CHCH₃), 0.91 (t, J_(H—H)=7.1 Hz, 3H, CH₂CH₃) ppm. ¹³C NMR (CDCl₃, 75 MHz, 298 K): δ 148.46 (i-C₆H₃), 144.64 (m-C₆H₃), 139.40 (p-C₆H₃), 108.75 (m-C₆H₃), 104.34 (OCH₂), 100.62 (o-C₆H₃), 95.90 (o-C₆H₃), 51.54, 34.94, 33.03, 32.00, 29.74, 27.06, 22.80, 18.20 (CH₃), 14.23 (CH₃) ppm.

FIG. 17 is a ¹H NMR spectrum (300 MHz, CDCl3, 298 K) of N-(2-methyloctyl)benzo[d][1,3]dioxol-5-amine. FIG. 18 is a ¹³C NMR spectrum (75 MHz, CDCl3, 298 K) of N-(2-methyloctypenzo[d][1,3]dioxol-5-amine.

N-(4-((tert-butyldimethylsilyl)oxy)-2-methylbutyl)aniline

N-methylaniline (54 mg, 0.5 mmol), (but-3-en-1-yloxy)(tert-butyl)dimethylsilane (93 mg, 0.5 mmol), Ta(CH₂SiMe₃)₃Cl₂ (13 mg, 0.025 mmol), L4 (8 mg, 0.025 mmol). Reaction time: 2 h. Yield 75%. ¹H NMR (CDCl₃, 300 MHz, 298 K): δ 7.20 (t, ³J_(H—H)=7.8, 2H, m-C₆H₄), 6.70 (td, ³J_(H—H)=0.9, 7.3, 1H, p-C₆H₄), 6.63 (d, ³J_(H—H)=8.5, 2H, o-C₆H₄), 3.85 (br s, 1H, NH), 3.83-3.64 (m, 2H, OCH₂), 3.10 (dd, J_(H—H)=6.3, 12.2 Hz, 1H, NC(H)H), 2.97 (dd, J_(H—H)=6.9, 12.2 Hz, 1H, NC(H)H), 1.97 (oct, J_(H—H)=6.7 Hz, 1H, OCH₂C(H)H), 1.76-1.61 (m, 1H, CHCH₃), 1.53-1.39 (m, 1H, OCH₂C(H)H), 0.95 (d, J_(H—H)=1.3 Hz, 9H, SiC(CH₃)₃), 0.10 (d, J_(H—H)=1.1 Hz, 6H, SiCH₃) ppm. ¹³C NMR (CDCl₃, 75 MHz, 298 K): δ 148.71 (i-C₆H₅), 129.33 (m-C₆H₅), 117.00 (p-C₆H₅), 112.74 (o-C₆H₅), 77.16 (OCH₂), 61.20 (NCH₂), 50.43 (OCH₂CH₂), 37.94, 29.98, 26.10 (SiC(CH₃)₃), 18.44 (CHCH₃), −5.18 (SiCH₃) ppm.

FIG. 19: ¹H NMR spectrum (300 MHz, CDCl3, 298 K) of 4-((tert-butyldimethylsilyl)oxy)-2-methylbutyl)aniline. FIG. 20 is a ¹³C NMR spectrum (75 MHz, CDCl3, 298 K) of 4-((tert-butyldimethylsilyl)oxy)-2-methylbutyl)aniline.

N-(2-cyclohexylpropyl)aniline

N-methylaniline (54 mg, 0.5 mmol), vinylcyclohexane (55 mg, 0.5 mmol), Ta(CH₂SiMe₃)₃Cl₂ (13 mg, 0.025 mmol), L4 (8 mg, 0.025 mmol). Reaction time: 2 h. Yield 86%. ¹H NMR (CDCl₃, 300 MHz, 298 K): δ 7.25-7.17 (m, 2H, m-C₆H₄), 6.79-6.69 (m, 1H, p-C₆H₄), 6.69-6.63 (m, 2H, o-C₆H₄) 3.87 (br s, 1H, NH), 3.20 (dd, J_(H—H)=5.5, 12.1 Hz, 1H, NC(H)H), 2.93 (dd, J_(H—H)=7.9, 12.1 Hz, 1H, NC(H)H), 1.87-1.60 (overlapping m, 6H, CH and CH₂ ^(Cy)), 1.47-1.04 (m, 6H, CH₂ ^(Cy)), 0.99 (d, J_(H—H)=6.9 Hz, 3H, CHCH₃) ppm.

N-((1-methylcyclohexyl)methyl)aniline

N-methylaniline (54 mg, 0.5 mmol), vinylcyclohexane (48 mg, 0.5 mmol), Ta(CH₂SiMe₃)₃Cl₂ (13 mg, 0.025 mmol), L4 (8 mg, 0.025 mmol). Reaction time: 3 h. Yield 99%. ¹H NMR (CDCl₃, 300 MHz, 298 K): δ 7.30-7.21 (m, 2H, m-C₆H₅), 6.82-6.66 (overlapping m, 3H, o-C₆H₅ and p-C₆H₅), 3.68 (br s, 1H, NH), 3.03 (s, 2H, NCH₂), 1.69-1.33 (overlapping m, 10H, CH₂ ^(Cy)), 1.08 (s, 3H, CH₃) ppm.

N-(2-(cyclohex-3-en-1-yl)propyl)aniline

N-methylaniline (54 mg, 0.5 mmol), vinylcyclohexane (55 mg, 0.5 mmol), Ta(CH₂SiMe₃)₃Cl₂ (13 mg, 0.025 mmol), L4 (8 mg, 0.025 mmol). Reaction time: 2 h. Yield 98%. ¹H NMR (CDCl₃, 300 MHz, 298 K): δ 7.28-7.17 (m, 2H, m-C₆H₅), 6.75 (t, J_(H—H)=6.8 Hz, 1H, m-C₆H₅), 6.67 (d, J_(H—H)=7.8 Hz, 1H, o-C₆H₅), 5.75 (s, 2H, CH═CH₂), 3.89 (br s, 1H, NH), 3.30-3.18 (m, 1H, NC(H)H), 3.05-2.92 (m, 1H, NC(H)H), 2.25-1.24 (overlapping m, 8H, CHCH₃, CH₂CH, and CH₂), 1.07-0.98 (m, 3H, CH₃) ppm. The chemical shifts for the title compound match those reported in the literature.

N-(2-methyl-4-phenylbutyl)aniline

N-methylaniline (54 mg, 0.5 mmol), 4-phenyl-1-butene (66 mg, 0.5 mmol), Ta(CH₂SiMe₃)₃Cl₂ (13 mg, 0.025 mmol), L4 (8 mg, 0.025 mmol). Reaction time: 3 h. Yield 87%. ¹H NMR (CDCl₃, 300 MHz, 298 K): δ 7.38-7.28 (m, 2H, m-C₆H₅), 7.27-7.15 (overlapping m, 5H, m-NC₆H₅, o-C₆H₅, and p-C₆H₅), 6.72 (t, J_(H—H)=7.1 Hz, 1H, p-NC₆H₅), 6.62 (d, J_(H—H)=7.9 Hz, 2H, o-NC₆H₅), 3.69 (br s, 1H, NH), 3.13 (dd, J_(H—H)=5.8, 12.3 Hz, 1H, NC(H)H), 2.97 (dd, J_(H—H)=6.9, 12.3 Hz, 1H, NC(H)H), 2.84-2.57 (m, 2H, C₆H₅CH₂), 1.92-1.75 (m, 2H, C₆H₅CH₂CH₂), 1.64-1.47 (m, 1H, CHCH₃), 1.08 (d, J_(H—H)=6.6 Hz, 2H, CHCH₃) ppm. The chemical shifts for the title compound match those reported in the literature.

N-(2-(4-chlorophenyl)propyl)aniline

N-methylaniline (54 mg, 0.5 mmol), 4-chlorostyrene (70 g, 0.5 mmol), Ta(CH₂SiMe₃)₃Cl₂ (13 mg, 0.025 mmol), L4 (8 mg, 0.025 mmol). Reaction time: 2 h. Yield 98%. ¹H NMR (CDCl₃, 300 MHz, 298 K): δ 7.31 (d, J_(H—H)=8.4 Hz, 2H, m-C₆H₄C₁), 7.23-7.14 (overlapping m, 4H, m-C₆H₄C₁ and o-C₆H₅), 6.72 (t, J_(H—H)=7.2 Hz, 1H, p-C₆H₅), 6.59 (d, J_(H—H)=8.5 Hz, 2H, o-C₆H₅), 3.59 (br s, 1H, NH), 3.35 (dd, J_(H—H)=6.1, 12.5 Hz, 1H, NC(H)H), 3.22 (dd, J_(H—H)=8.2, 12.4 Hz, 1H, NC(H)H), 3.13-2.99 (m, 1H, CHCH₃), 1.33 (d, J_(H—H)=6.9 Hz, 3H, CHCH₃) ppm.

N-(2-(2-bromophenyl)propyl)aniline (A) and N-(3-(2-bromophenyl)propyl)aniline (B)

N-methylaniline (54 mg, 0.5 mmol), 2-bromostyrene (92 mg, 0.5 mmol), Ta(CH₂SiMe₃)₃Cl₂ (13 mg, 0.025 mmol), L4 (8 mg, 0.025 mmol). Reaction time: 2 h. Yield 65%. ¹H NMR (CDCl₃, 300 MHz, 298 K): Product is a combination of linear and branched HAA products (˜9:1), additional spectra are required for full peak assignments.

FIG. 21 is a ¹H NMR spectrum (300 MHz, CDCl₃, 298 K) of a mixture between N-(2-(2-bromophenyl)propyl)aniline and N-(3-(2-bromophenyl)propyl)aniline.

N-(2-methyl-3-phenylpropyl)aniline (A) and N-(2-phenylbutyl)aniline (B)

N-methylaniline (54 mg, 0.5 mmol), cis/trans-β-methylstyrene (60 mg, 0.5 mmol), Ta(CH₂SiMe₃)₃Cl₂ (13 mg, 0.025 mmol), L5 (8 mg, 0.025 mmol). Reaction time: 48 h. Yield 78%. ¹H NMR (CDCl₃, 300 MHz, 298 K): δ 7.42-7.12 (overlapping m, 14H, m-C₆H₅ ^(A), m-NC₆H₅ ^(A), o,p-C₆H₅ ^(A), o,m,p-C₆H₅ ^(B), and m-NC₆H₅ ^(B)), 6.79-6.52 (overlapping m, 6H, p-NC₆H₅ ^(A), o-NC₆H₅ ^(A), p-NC₆H₅ ^(B), and o-NC₆H₅ ^(B)), 3.69 (br s, 1H, NH^(A)), 3.60-3.38 (overlapping m, 2H, NH^(B) and NC(H)H^(B)), 3.30-3.19 (m, 1H, NC(H)H^(B)), 3.13 (dd, J_(H—H)=6.0, 12.4 Hz, 1H, NC(H)H^(A)), 2.98 (dd, J_(H—H)=6.9, 12.3 Hz, 1H, NC(H)H^(A)), 2.87-2.75 (m, 1H, C₆H₅CH^(B)), 2.79 (dd, J_(H—H)=6.3, 13.4 Hz, 1H, C₆H₅C(H)H^(A)), 2.53 (dd, J_(H—H)=6.3, 13.4 Hz, 1H, C₆H₅C(H)H^(A)), 2.18-2.03 (m, 1H, CHCH₃ ^(A)), 1.92-1.77 (m, 1H, C(H)HCH₃ ^(B)), 1.77-1.60 (m, 1H, C(H)HCH₃ ^(B)) 1.01 (d, J_(H—H)=6.7 Hz, CHCH₃ ^(A)) ppm.

N-(cyclohexylmethyl)aniline

N-methylaniline (54 mg, 0.5 mmol), cyclohexene (41 mg, 0.5 mmol), Ta(CH₂SiMe₃)₃Cl₂ (13 mg, 0.025 mmol), L5 (8 mg, 0.025 mmol). Reaction time: 20 h. Yield 70%. ¹H NMR (CDCl₃, 300 MHz, 298 K): δ 7.23-7.11 (m, 1H, m-C₆H₅), 6.68 (t, J_(H—H)=7.2 Hz, 1H, p-C₆H₅), 6.60 (d, J_(H—H)=8.9 Hz, 2H, o-C₆H₅), 3.70 (br s, 1H, NH), 2.96 (d, J_(H—H)=6.7 Hz, NCH₂), 1.93-1.67 (m, 5H, CH₂), 1.68-1.52 (m, 1H, CH), 1.39-1.21 (m, 3H, CH₂), 1.11-0.93 (m, 1H, CH₂) ppm. The chemical shifts for the title compound match those previously reported in the literature.Error! Bookmark not defined.^(k,l)

N-(cyclopentylmethyl)aniline

N-methylaniline (54 mg, 0.5 mmol), cyclopentene (34 mg, 0.5 mmol), Ta(CH₂SiMe₃)₃Cl₂ (13 mg, 0.025 mmol), L5 (8 mg, 0.025 mmol). Reaction time: 20 h. Yield 74%. ¹H NMR (CDCl₃, 300 MHz, 298 K): δ 7.21 (t, J_(H—H)=7.5 Hz, 2H, m-C₆H₅), 6.72 (t, J_(H—H)=7.3 Hz, 1H, p-C₆H₅), 6.65 (d, J_(H—H)=7.7 Hz, 2H, o-C₆H₅), 3.69 (br s, 1H, NH), 3.06 (d, J_(H—H)=7.3 Hz, 2H, NCH₂), 2.19 (hept, J_(H—H)=7.6 Hz, 1H, NCH₂CH), 1.94-1.80 (m, 2H, CH₂), 1.77-1.52 (m, 4H, CH₂), 1.40-1.23 (m, 2H, CH₂) ppm.

N-(cycloheptylmethyl)aniline

N-methylaniline (54 mg, 0.5 mmol), cycloheptene (49 mg, 0.5 mmol), Ta(CH₂SiMe₃)₃Cl₂ (13 mg, 0.025 mmol), L5 (8 mg, 0.025 mmol). Reaction time: 6 h. Yield 88%. ¹H NMR (400 MHz, CDCl₃): δ 7.17 (t, J=7.4 Hz, 2H), 6.70 (t, J=7.2 Hz, 1H), 6.62 (d, J=8.0 Hz, 2H), 3.76 (br s, 1H), 2.97 (d, J=6.3 Hz, 2H), 1.90-1.40 (m, 11H), 1.35-1.20 (m, 2H).

EXAMPLES

Various alternative embodiments and examples are described herein. These embodiments and examples are illustrative and should not be construed as limiting the scope of the invention. In particular, while tantalum was used as the representative group 5 metal for these studies, the skilled person will expect other group 5 metals, and especially niobium, to perform similarly.

Example 1: Group 5 Metal-Based Precursors as Catalysts

In order to identify potentially promising group 5 metal/ligand salt combinations, the most common Ta precursors were screened in the absence of any ligand salt (Table 1). For this step, the standard benchmark reaction between N-methylaniline and 1-octene was chosen. It has previously been demonstrated that TaMe₃Cl₂ can catalyse this reaction, reaching a conversion of 91%, after 30 hours at 110° C. using a 10 mol % catalyst loading, but full conversion could never be achieved due to catalyst decay. Hence, optimization of the benchmark reaction was started by reducing the reaction time from 24 h to only 1 h. Under these conditions TaMe₃Cl₂ could afford a 28% conversion. Further catalytic screening confirmed that Ta-alkyl precursors can competently catalyse the addition of N-methylaniline to 1-octene, with Ta(CH₂SiMe₃)₃Cl₂ showing the most promising activity, achieving 39% conversion in only 1 h, when stoichiometric amounts of substrates were used. On the other hand, complexes bearing a Ta—NMe₂ moiety were far less reactive, at best showing a 15% conversion after 24 hours of reaction. These data illustrated the promising catalytic activity of Ta(CH₂SiMe₃)₃Cl₂. For this reason, Ta(CH₂SiMe₃)₃Cl₂ was chosen as the tantalum precursor for all subsequent catalytic experiments.

TABLE 1 Screening of Ta precursors for intermolecular hydroaminoalkylation reactions.^(a)

Ta(CH₂SiMe₃)₃Cl₂ 1 h, 39% Ta(CH₂CMe₃)₃Cl₂ 25 h, 15% TaMe₃Cl₂ 1 h, 28% Ta(NMe₂)₅ 24 h, n.r. [Ta(NMe₂)₃Cl₂]₂ 1 h, n.r. 24 h, 15% ^(a)Reaction conditions: amine (0.5 mmol), 1-octene (0.5 mmol), [Ta] precatalyst (0.025 mmol), d₈ toluene (0.6 mL). Conversion determined by ¹H NMR spectroscopy. n.r. = no reaction.

Example 2: Ligand Salt Screening Using In-Situ Experiments

Further catalytic experiments were performed by generating in situ the catalytic species by reacting Ta(CH₂SiMe₃)₃Cl₂ with a variety N,O-chelate type ligand salts.

This study was extended to internal alkenes, adding the more challenging cyclohexene to the pool of substrates. In an effort to perform the catalytic screening under milder conditions, the reaction temperature for reactions using cyclohexene as a substrate were lowered from 145° C. to 130° C. For this step, attention was focussed on amidate (Table 2, L1), phosphoramidate (Table 2, L2), and pyridonate (Table 2, L3) sodium salts. In addition, a variety of ureate type ligand salts were also investigated. The latter type of ligands have previously been studied with group 4 metals for hydroamination and alkyne dimerization catalysis. Catalytic screening of in situ mixtures containing L1 and L2 resulted in no or poor conversion, regardless of the alkene substrate or the chosen reaction time. This behaviour is somewhat surprising considering that in the case of 1-octene, the related amidate-Ta(NMe₂)₄ complex gave a 96% conversion of the addition product after 63 h of reaction time. Moreover, the in situ mixture between the ligand salt L2 and TaMe₃Cl₂ afforded 52% conversion after 20 h, at room temperature. On the other hand, using the less sterically encumbered pyridonate ligand salt L3 proved to be more successful as 31% and 33% conversions were observed for terminal and internal alkene substrates, respectively.

TABLE 2 Screening of ligand salts in hydroaminoalkylation reactions.^(a)

Ligand Salt Alkene

L1  1 h, n.r. 20 h, n.r.

L2  1 h, n.r. 20 h, n.r.

L3  1 h, 31% 20 h, 33%

L4  1 h, 55% 24 h, 58%^(d)

L5  1 h, 37% 20 h, 34%

L6  1 h, 83% 20 h, 19%

L7  1 h, 12% 20 h, 83%

L8  1 h, 5% 20 h, 6%

L9  1 h, 48% 20 h, 45%

L10 1 h, 45% n/a

L11 1 h, traces n/a

L12 1 h, 93% n/a

L13 1 h, 92% n/a ^(a)Reaction conditions: amine (0.5 mmol), alkene (0.5 mmol), Ta(CH₂SiMe₃)₃Cl₂ (0.025 mmol), ligand salt (0.025 mmol), d₈-toluene (0.5 g). Conversion was determined by ¹H NMR spectroscopy. n.r. = no reaction. All reactions with 1-octene were performed at 110° C., while those with cyclohexene were performed at 130° C.

Next, ureate salts were tested. In situ catalyst system with L6 was excellent, affording 83% conversion in only 1 h for the reaction between 1-octene and N-methylaniline with a TOF of more than 16 h⁻¹. However, when the more challenging cyclohexene substrate was evaluated, only a modest 19% conversion was observed after 20 h. Remarkably, the mixed aryl/alkyl-substituted ureate ligand L7 resulted in a reversed trend; this system provided higher conversion of the internal alkene substrate (20 h, 83%), but was less effective for the terminal alkene substrate (1 h, 12%). These results are surprising considering that the only change is the N-Ph group of L6 to the N-iPr moiety in L7. Exchanging the remaining Ph group of L7 with an iPr group (L8) did not improve the catalytic system and poor conversions were obtained for both alkenes. Without wishing to be bound by an particular theory, the inventors propose that that the known hemilability of N,O-chelating ligands coupled with the variable coordination modes of ureate ligands results in a flexible coordination environment about the reactive metal center, thereby promoting reactivity.

Table 3 provides additional data with respect to the effect of various ureate ligand salts on the addition of N-methylaniline to 1-octene.

TABLE 3 Screening of ligand salts in hydroaminoalkylation reactions in which N- methylaniline is added to 1-octene.

Temperature Time Conversion Ligand (° C.) (h) (%)

110 1 55

110 2 95

110 1 23

110 1 5

110 1 37

110 1 48

110 1 45

110 1 0

110 1 99

110 1 40

110 1 20

110 1 30

110 24 100

110 1 31

110 0.25 67

110 0.5 87

110 1 93

110 0.5 36

Table 4 provides additional data with respect to the effect of various ureate ligand salts on the addition of N-methylaniline to cyclohexene.

TABLE 4 Screening of ligand salts in hydroaminoalkylation reactions in which N- methylaniline is reacted with cyclohexene.

Temperature Time Conversion Ligand (° C.) (h) (%)

145 24 58

130 20 35

130 20 83

145 20  6

145 20 34

130 20 45

130 20  0

130 20  0

150 20 82

130 20 20

130 20 70

130 20 42

Example 3: Amine Substrate Scope

The study referred to in Tables 2 and 3 was extended by broadening the substrate scope in amine substrates. 1-Octene was kept as the preferred substrate for the terminal alkenes, whereas cyclohexene was swapped with cyclooctene, due to higher reactivity caused by the ring strain. As indicated in Table 5, catalytic mixtures including L6 were used to convert the terminal alkene, while ligand salt L7 was used exclusively for the internal alkene. Another objective was to purify the final products in an easy manner, by avoiding separation on the chromatographic column. For this reason, reaction times were adapted in order to favour full substrate conversion i.e. 2 h for 1-octene and 6 h for cyclooctene. As expected, the reaction between N-methylaniline and 1-octene (Table 5, Entry 1), resulted in a nearly complete conversion of the substrates with a TOF value of 9.5 h⁻¹. Likewise, cyclooctene was fully converted within 6 hours, with an average of 3.3 turnovers per hour and an excellent 83% isolated yield (Table 5, Entry 1 b). The pyridonate-Ta(NMe₂)₃Cl₂ complex can also catalyse this reaction, but in this case longer reaction times are needed (20 h), with a TOF value limited to 1 h⁻¹. ^(Error! Bookmark not defined.I) Consistently with results reported in the literature, para-substituted N-methylanilines are well tolerated and good TOF values were recorded for both 1-octene (3-3.3 h⁻¹) and cyclooctene (8.8-10 h⁻¹) substrates. On the same note, the presence of halide substituents on the aromatic ring (Table 5, Entries 3-5) does not inhibit the reaction rates, opening the way for further functionalization via cross-coupling or nucleophilic aromatic substitution reactions. Perhaps more importantly, the potential pharmaceutically relevant aniline N-methyl-4-(trifluoromethoxy)aniline (Table 5, Entry 6) proved to be highly reactive under the specified catalytic conditions. Impressively, the presence of a dioxole unit was also well tolerated, as the corresponding addition product was easily obtained with an 85% yield.

TABLE 5 Substrate scope in amine^(a)

Isolated Entry Amine Alkene Yield (%)  1  2

a b 88 83  3  4

a b 77 70  5  6

a b 86 95  7  8

a b 90 93  9 10

a b 85 88 11 12

a b 92 85 13

a 85 ^(a)Reaction conditions: amine (0.5 mmol), alkene (0.5 mmol), Ta(CH₂SiMe₃)₃Cl₂ (0.025 mmol), ligand salt (0.025 mmol), d₈-toluene (0.5 g). L4 was used for all terminal alkene substrates at 110° C. over 2 h and L5 was used for internal alkene substrates at 130° C. over 6 h.

Table 6 provides additional data with respect to the addition of various amines to 1-octene in the presence of tantalum metal complexes.

TABLE 6 Amine scope for hydroaminoalkylation reactions.

Temperature Time Conversion Entry Amine Alkene (° C.) (h) (%) dr  1

150 20 100 16:1  2

150 20  65 >20:1   3

150 20 >20:1   4

150 20 100 10:1  5

150 20 100 >20:1   6

150 20 100  8:1  7

150 20 100 >20:1   8

n/a 150 20 100 n/a  9

150 20 100 1:1 regioisomers dr >20:1 10

150 20 100 >20:1  11

110 20  90 TBD 12

150 20 100 dr TBD 13

150 20  50 dr TBD 14

150  2 100 >20:1 Mostly bis- alkylated product obtained 15

150 20 100 1.79:1 (Branched:Linear regioisomers) dr 17:1 16

150 20 100 1.2:1 (Branched:Linear regioisomers) dr 19:1

Example 4: Alkene Substrate Scope

Having tested the capability of the Ta(CH₂SiMe₃)₃Cl₂ containing catalytic system in broadening the substrate scope in amines, attention was switched to the alkene class of substituents (Table 7). In this respect, a variety of terminal, di-substituted alkenes and dienes were chosen as candidates. As before, L6 was used exclusively for terminal alkenes, while L7 was used in the case of the internal ones. Alkenes containing silyl protected OH moieties were easily reacted with N-methylaniline in less than 2 h to give the addition product in a 75% yield, and with an average of 8.6 turnovers per hour. Further catalytic screenings involved trimethyl(vinyl)silane, which upon reaction with N-methylaniline gives a 1:1 mixture (TOF=9.0 h⁻¹) between the branched and linear product, perhaps as a consequence of the 6-silicon effect. Even sterically hindered alkenes such as vinylcyclohexene and methylenecyclohexane are accommodated giving the corresponding addition products in excellent yields and TOF values of 9.1 h⁻¹ and 6.6 h⁻¹, respectively. Remarkably, 4-vinylcyclohex-1-ene was highly reactive under catalytic conditions (99% yield, TOF=10 h⁻¹), when only the terminal C═C bond was selectively activated. This result is impressive as isolated dienes are particularly difficult to convert. Styrenes are no exception to the active class of substituents as 4-chlorostyrene and 2-bromo-styrene reacted quantitatively (TOF=10 and 10 h⁻¹) with the amine, with no signs of polymerized product being observed. In the case of 2-bromo-styrene, the presence of the halide atom in the ortho position on the aryl ring notably does not sterically affect the outcome of the reaction. This observation is counterintuitive considering that under identical conditions, 2-methylstyrene was found to be completely inert.

The substrate scope containing the more challenging internal alkenes was investigated next. First, α-methylstyrene required long reaction times (48 h) to ensure an almost complete conversion. α-methylstyrene can be fully converted in 24 h when the catalyst is supported by the smaller pyridonate type of ligands. The reactivity of cyclic internal alkenes was found to be directly proportional to the size of the ring, and therefore dependant on the ring strain. Hence, cyclooctene was found to be the most reactive (TOF=3.2 h⁻¹), followed by cycloheptene (TOF=3 h⁻¹), while cyclopentene (TOF=0.79 h⁻¹) and cyclohexene (TOF=0.80 h⁻¹) displayed a similar reactivity. Absence of the ring strain, as observed for the internal linear alkenes had a clear impact on the reactivity of these substrates. Indeed, compared to the cyclic alkenes, only moderate yields were obtained after 20 h i.e. 4-octene (55%), cis-3-hexene (55%), trans-3-hexene (32%).

TABLE 7 Substrate scope in alkene.^(a,b) Turnover frequency values (h⁻¹) are given in brackets. Ratio of branched:linear regioisomers are given in square brackets

L6

L7

^(a)Reaction conditions: amine (0.5 mmol), alkene (0.5 mmol), Ta(CH₂SiMe₃)₃Cl₂ (0.025 mmol), ligand salt (0.025 mmol), d₈-toluene (0.5 g). Conversion determined by ¹H NMR spectroscopy. All reactions with terminal alkene substrates we're performed with L6 at 110 ° C. Reactions with internal alkene substrates were performed with L7 at 130° C. ^(b)Major isomer presented, yield refers to combined regioisomers.

Table 8 provides additional data with respect to the addition of N-methyl butylamine to various alkenes.

TABLE 8 Addition of various alkenes to N-methyl butylamine.

Temperature Time Conversion Entry Alkene (° C.) (h) (%) 1

110 24 94 2

145 24 94 3

110 24 50 4

145 24  0 5

145  1  0 6

145 24 78

Table 9 provides additional data with respect to the effect of various ureate ligand salts and metal complexes on the addition of piperidine to styrene.

TABLE 9 Screening of ligand salts in hydroaminoalkylation reactions in which piperidine is reacted with styrene.

Temperature Time Percent Entry Ligand (° C.) (h) Conversion A:B dr 1

150 20 100 1.71:1 16:1 2

150 20 100 2:1 20:1 3

150 20 100 2.2:1 18:1 4

150 20 100 1.7:1 15:1 5

150 20 100 1.4:1 18:1

Example 5: Hydroamination Reaction Between Piperidine and 1-Octene

Tables 10 and 11 provide data with respect to the effect of various ureate ligand salts and metal complexes on the addition of piperidine to 1-octene.

TABLE 10 Hydroaminoalkylation data using cyclic ureate salts and Ta(CH₂SiMe₃)₃Cl₂ for the reaction between piperidine and 1-octene.

Ligand salt Time (h) Conversion (%)

144 100

144 100 Temperature Time Conversion Ligand (° C.) (h) (%)

150 6  0

150 6 100

150 6 100

150 6 100

150 6 100

150 6  37

Example 6. Effect of Temperature on Hydroaminoalkylation

FIGS. 43 and 44 illustrate that the rate of the hydroaminoalkylation reaction for aryl and alkyl amines with 1-octene in the presence of metal complexes disclosed herein is temperature dependent and increases with temperature from 70° C. to 100° C.

Example 8. Effect of Catalyst Concentration on Hydroaminoalkylation

FIG. 45 illustrates that the rate of the hydroaminoalkylation reaction for alkyl amines with 1-octene in the presence of metal complexes disclosed herein is concentration dependent and increases with concentration 2 mol % to 10 mol %.

Example 7. Effect of Halide Salts on Hydroaminoalkylation

FIG. 46 illustrates that the rate of the hydroaminoalkylation reaction for aryl amines with 1-octene in the presence of metal complexes disclosed herein increases with the addition of halide salts. FIGS. 47 and 48 demonstrate that the rate of the hydroaminoalkylation reaction for aryl amines with 1-octene in the presence of metal complexes disclosed herein increases with the addition of KBr at temperatures from 70° C. to 100° C.

Operation

While specific embodiments of the invention have been described and illustrated, such embodiments should be considered illustrative of the invention only and not as limiting the invention as construed in accordance with the accompanying claims. 

What is claimed is:
 1. A metal complex having the structure of Formula I:

wherein: R¹ and R² are: each independently: H; a C₁-C₄₀ substituted or unsubstituted linear, branched or cyclic alkyl or alkenyl or alkynyl; a substituted or unsubstituted aryl; or a substituted or unsubstituted heterocyclic group; or bonded together thereby forming, together with the nitrogen atom they are both bound to, a heterocycle; R³: is H; a C₁-C₄₀ substituted or unsubstituted linear, branched or cyclic alkyl or alkenyl or alkynyl; or a substituted or unsubstituted aryl; or a substituted or unsubstituted heterocyclic group; or bonded together with R¹ and/or R² to form a heterocycle. M is a group 5 metal; a=0 to 4 and b=0 to 4, wherein the sum of a and b is 4; each X is a halogen substituent; each R⁴ is independently: H; or a C₁-C₂₀ substituted or unsubstituted, linear, branched or cyclic alkyl, optionally comprising heteroatoms.
 2. The metal complex of claim 1, wherein each X is independently Cl or Br.
 3. The metal complex of claim 1 or 2, wherein a=1 or a=2.
 4. The metal complex of claim 1, 2, or 3, wherein R¹ and R² are each independently: methyl; ethyl; isopropyl; cyclohexyl; phenyl; 2,6-dimethyl phenyl; 2,4,6-trimethyl phenyl; 4-methyl phenyl; optionally substituted piperidine; optionally substituted pyrrolidine; or substituted morpholine.
 5. The metal complex of claim 1, 2, or 3, wherein R¹ and R² are bonded together to form, together with the nitrogen atom they are both bound to, a 6-membered ring, which optionally may be substituted.
 6. The metal complex of claim 1, 2, or 3, wherein: R¹ and R² are each phenyl; R¹ is phenyl and R² is isopropyl; R¹ and R² are bonded together to form, together with the nitrogen atom they are both bound to, piperidinyl; R¹ is phenyl and R² is methyl; R¹ is methyl and R² is 1-phenylethyl; R¹ is methyl and R² is isopropyl; or R¹ is phenyl and R² is diphenylmethyl.
 7. The metal complex of any one of claims 1 to 5, wherein R³ is: phenyl; 2,6-dimethyl phenyl; 2,6-di(isopropyl) phenyl; or


8. The metal complex of claim 1, 2, or 3, wherein R³ is bonded together with R¹ and/or R² to form, together with each of the nitrogen atoms they are bound to, a 5-membered ring, which optionally may be substituted.
 9. The metal complex of claim 8, wherein R³ is bonded together with R¹ and/or R², and each of the nitrogen atoms they are bound to, to form:


10. The metal complex of any one of claims 1 to 9, wherein R⁴ is —CH₃, —NMe₂, —CH₂C(CH₃)₃, or —CH₂Si(CH₃)₃.
 11. The metal complex of any one of claims 1 to 10, wherein M is tantalum (Ta).
 12. The metal complex of any one of claims 1 to 10, wherein M is niobium (Nb).
 13. The metal complex of any one of claims 1 to 10, wherein M is vanadium (V).
 14. A metal complex having the structure of Formula II

wherein: R¹ and R² are: each independently: methyl; ethyl; isopropyl; cyclohexyl; phenyl; 2,6-dimethyl phenyl; 2,4,6-trimethyl phenyl; 4-methyl phenyl; optionally substituted piperidine; optionally substituted pyrrolidine; or substituted morpholine; or bonded together to form, together with the nitrogen atom they are both bound to, a 6-membered ring, which optionally may be substituted; R³ is: phenyl; 2,6-dimethyl phenyl; or 2,6-di(isopropyl) phenyl; or bonded together with R¹ and/or R² to form, together with each of the nitrogen atoms they are bound to, a 5-membered ring, which optionally may be substituted; each X is independently Cl or Br; a=1 or 2 and b=(4−a); and R⁴ is —CH₃, —NMe₂, —CH₂C(CH₃)₃, or —CH₂Si(CH₃)₃.
 15. A metal complex, which metal complex is:


16. A catalyst comprising a metal complex as defined in any one of claims 1 to
 15. 17. A catalyst kit comprising at least one metal complex as defined in any one of claims 1 to 15 and a quenching agent.
 18. The catalyst kit of claim 17, wherein the quenching agent includes an alcohol, water, or a combination thereof.
 19. A method of synthesizing a metal complex of Formula I, the method comprising reacting a group 5 metal salt of Formula VII with one equivalent of an amide of Formula VIII according to the following reaction:

wherein: R¹ and R² are: each independently: H; a C₁-C₄₀ substituted or unsubstituted linear, branched or cyclic alkyl or alkenyl or alkynyl; a substituted or unsubstituted aryl; or a substituted or unsubstituted heterocyclic group; or bonded together thereby forming, together with the nitrogen atom they are both bound to, a heterocycle; R³: is H; a C₁-C₄₀ substituted or unsubstituted linear, branched or cyclic alkyl or alkenyl or alkynyl; or a substituted or unsubstituted aryl; or a substituted or unsubstituted heterocyclic group; or bonded together with R¹ and/or R² to form a heterocycle. M is a group 5 metal; a=0 to 4 and b=0 to 4, wherein the sum of a and b is 4; c=1 to 5 and d=0 to 4, wherein the sum of c and d is 5; each X is a halogen substituent; each R⁴ is independently: H; or a C₁-C₂₀ substituted or unsubstituted, linear, branched or cyclic alkyl, optionally comprising heteroatoms.
 20. The method of claim 19, wherein X is independently Cl or Br.
 21. The method of claim 19 or 20, wherein a=1 or a=2.
 22. The method of claim 19, 20, or 21, wherein R¹ and R² are each independently: methyl; ethyl; isopropyl; cyclohexyl; phenyl; 2,6-dimethyl phenyl; 2,4,6-trimethyl phenyl; 4-methyl phenyl; optionally substituted piperidine; optionally substituted pyrrolidine; or substituted morpholine.
 23. The method of claim 19, 20, or 21, wherein: R¹ and R² are each phenyl; R¹ is phenyl and R² is isopropyl; R¹ and R² are bonded together to form, together with the nitrogen atom they are both bound to, piperidinyl; R¹ is phenyl and R² is methyl; R¹ is methyl and R² is 1-phenylethyl; R¹ is methyl and R² is isopropyl; or R¹ is phenyl and R² is diphenylmethyl.
 24. The method of claim 19, 20, or 21, wherein R¹ and R² are bonded together to form, together with the nitrogen atom they are both bound to, a 6-membered ring, which optionally may be substituted.
 25. The method of any one of claims 19 to 24, wherein R³ is: phenyl; 2,6-dimethyl phenyl; 2,6-di(isopropyl) phenyl; or


26. The method of claim 19, 20, or 21, wherein R³ is bonded together with R¹ and/or R² to form, together with each of the nitrogen atoms they are bound to, a 5-membered ring, which optionally may be substituted.
 27. The method of claim 26, wherein R³ is bonded together with R¹ and/or R², and each of the nitrogen atoms they are bound to, to form:


28. The method of any one of claims 19 to 27, wherein R⁴ is —CH₃, —NMe₂, —CH₂C(CH₃)₃, or —CH₂Si(CH₃)₃.
 29. The method of any one of claims 19 to 28, wherein M is tantalum (Ta).
 30. The method of any one of claims 19 to 28, wherein M is niobium (Nb).
 31. The method of any one of claims 19 to 28, wherein M is vanadium (V).
 32. The method of any one of claims 19 to 31, wherein the reaction is performed in a temperature range from −30° C. to ambient temperature.
 33. The method of any one of claims 19 to 32, wherein the reaction is performed at ambient temperature.
 34. The method of claim 33, wherein ambient temperature is room temperature.
 35. The method of any one of claims 19 to 34, wherein the reaction is performed in an organic solvent.
 36. The method of claim 35, wherein the organic solvent is toluene or hexane.
 37. The method of claim 35, wherein the organic solvent is toluene.
 38. The method of any one of claims 19 to 37, comprising a further reaction step that is performed in situ.
 39. A method for α-alkylation of a secondary amine-containing moiety, the method comprising: (i) reacting said secondary amine-containing moiety with an olefin in the presence of a metal complex as defined in any one of claims 1 to
 15. 40. The method of claim 39, further comprising: (ii) isolating a product formed in step (i).
 41. The method of claim 39 or 40, wherein the secondary amine-containing moiety comprises at least two α-sp³ hybridized C—H bonds.
 42. The method of claim 39, 40, or 41, wherein the secondary amine-containing moiety is a C₄-C₁₀₀ linear, branched, or cyclic alkyl, optionally substituted and/or comprising heterotaoms.
 43. The method of any one of claims 39 to 42, wherein the secondary amine-containing moiety is substituted with a halogen, an ether, another amine, an alkyl, an alkene, an acetal, a phosphine, an amide, an alkyne, an imine, a nitrile, an isocyanide, an epoxide, a boronic acid ester; a phenyl that optionally may be substituted and/or part of a condensed ring system, or any combination thereof.
 44. The method of any one of claims 39 to 43, wherein the olefin comprises from 2 to 100 carbon atoms.
 45. The method of any one of claims 39 to 44, wherein the olefin comprises an internal alkene.
 46. The method of any one of claims 39 to 45, wherein the olefin is a linear or a cyclic olefin.
 47. The method of any one of claims 39 to 46, wherein the olefin comprises a terminal alkene.
 48. The method of any one of claims 39 to 46, wherein the olefin is an optionally substituted 1-alkene or an optionally substituted cycloalk-1-ene.
 49. The method of any one of claims 39 to 48, wherein the olefin comprises one or more protected functional group(s).
 50. The method of claim 39 or 40, wherein the olefin is:


51. The method of any one of claims 39 to 47, wherein the secondary amine-containing moiety is: pyrrolidine; piperidine;

wherein Z is H, OCF₃, F, Cl, Br, I, or OCH₃.
 52. The method of any one of claims 39 to 47, wherein the secondary amine-containing moiety is:


53. The method of any one of claims 39 to 52, wherein the reaction conditions comprise a reaction temperature in the range from 50° C. to 200° C.
 54. The method of any one of claims 39 to 52, wherein the reaction conditions comprise a reaction temperature in the range from 75° C. to 165° C.
 55. The method of any one of claims 39 to 52, wherein the reaction conditions comprise a reaction temperature in the range from 90° C. to 150° C.
 56. The method of any one of claims 39 to 52, wherein the reaction conditions comprise a reaction temperature in the range from range from 110° C. to 130° C.
 57. The method of any one of claims 39 to 52, wherein the reaction conditions comprise a reaction temperature of about 110° C.
 58. The method of any one of claims 39 to 52, wherein the reaction conditions comprise a reaction temperature of about 130° C.
 59. The method of any one of claims 39 to 52, wherein the reaction conditions comprise a solvent.
 60. The method of claim 59, wherein the solvent is non-protic.
 61. The method of claim 59, wherein the solvent is toluene, benzene, or a mixture thereof.
 62. The method of claim 59, wherein the solvent comprises toluene.
 63. The method of any one of claims 39 to 62, wherein, in step (i), the secondary amine-containing moiety and said olefin are in a stoichiometric ratio from 0.1 to 1.5.
 64. The method of any one of claims 39 to 62, wherein, in step (i), the secondary amine-containing moiety and said olefin are in a stoichiometric ratio of about 1:1.
 65. A method of synthesizing a pharmaceutical compound or an agrochemical compound, the method comprising α-alkylation of a secondary amine-containing moiety according to a method as defined in any one of claims 39 to
 64. 66. Use of a group 5 metal salt of Formula VII MX_(c)R⁴ _(d)  (Formula VII) wherein: M is a group 5 metal; c=1 to 5 and d=0 to 4, wherein the sum of c and d is 5; and each R⁴ is independently: H; or a C₁-C₂₀ substituted or unsubstituted, linear, branched or cyclic alkyl, optionally comprising heteroatoms, in combination with an amide of Formula VIII

wherein: R¹ and R² are: each independently: H; a C₁-C₄₀ substituted or unsubstituted linear, branched or cyclic alkyl or alkenyl or alkynyl; a substituted or unsubstituted aryl; or a substituted or unsubstituted heterocyclic group; or bonded together thereby forming, together with the nitrogen atom they are both bound to, a heterocycle; and R³: is H; a C₁-C₄₀ substituted or unsubstituted linear, branched or cyclic alkyl or alkenyl or alkynyl; or a substituted or unsubstituted aryl; or a substituted or unsubstituted heterocyclic group; or bonded together with R¹ and/or R² to form a heterocycle. for synthesizing a catalyst for α-alkylation of a secondary amine-containing moiety.
 67. The use of claim 66, wherein the catalyst is a metal complex of Formula I,

wherein a=0 to 4 and b=0 to 4, wherein the sum of a and b is
 4. 68. The use of claim 66 or 67, wherein α-alkylation of a secondary amine-containing moiety comprises reacting said secondary amine-containing moiety with an olefin in the presence of the catalyst.
 69. The use of claim 68, wherein the secondary-amine containing moiety is as defined in claim 50 or 51, and/or the olefin is as defined in any one of claims 44 to
 50. A kit for synthesizing a catalyst for α-alkylation of a secondary amine-containing moiety, the kit comprising: a group 5 metal salt of Formula VII: MX_(c)R⁴ _(d)  (Formula VII) wherein: M is a group 5 metal; c=1 to 5 and d=0 to 4, wherein the sum of c and d is 5; and each R⁴ is independently: H; or a C₁-C₂₀ substituted or unsubstituted, linear, branched or cyclic alkyl, optionally comprising heteroatoms, and an amide of Formula VIII:

wherein: R¹ and R² are: each independently: H; a C₁-C₄₀ substituted or unsubstituted linear, branched or cyclic alkyl or alkenyl or alkynyl; a substituted or unsubstituted aryl; or a substituted or unsubstituted heterocyclic group; or bonded together thereby forming, together with the nitrogen atom they are both bound to, a heterocycle; and R³: is H; a C₁-C₄₀ substituted or unsubstituted linear, branched or cyclic alkyl or alkenyl or alkynyl; or a substituted or unsubstituted aryl; or a substituted or unsubstituted heterocyclic group; or is bonded together with R¹ and/or R² to form a heterocycle. 